THE  UNIVERSITY 


OF  ILLINOIS 
LIBRARY 

02Co^ 


REMOTE  STORAGE 


CENTRAL  CIRCULATION  BOOKSTACKS 

The  person  charging  this  material  is  re- 


' sponsible  for  its  return  to  the  library  from 
which  it  was  borrowed  on  or  before  the 
Latest  Date  stamped  below. 

Theft,  mutiletiorv  and  underlining  of  books  are  reosons 
for  disciplinory  action  and  may  result  In  dismissal  from 
the  University. 

TO  RENEW  CALL  TELEPHONE  CENTER,  333-8400 

UNIVERSITY  OF  ILLINOIS  LIBRARY  AT  URBANA-CHAMPAIGN 


When  renewing  by  phone,  write  new  due  date  below 


previous  due  date. 


L162 


Digitized  by  the  Internet  Archive . 
in  2017  with  funding  from 

University  of  Illinois  Urbana-Champaign  Alternates 


: ija- 


https://archive.org/details/manualofprincipa00wleg_5 


Lifmm' 

Of  THE 


4 


Miidt'  l)y 

W.,  .V  '{irilT'RILilhi'T, 


T’ISW'iY.  R,  T 


OF  THE  PRINCIPAL 


INSTRUMENTS 


USED  IN 


Jimfrifan  dpiiginening  aiiij  Swrljegiitg, 

MANUFACTURED  BY 

W.  & L.  E.  GURLEY. 

THE  LIBRARY  RF  THE 

tJSlVEfiSlTy  OF  JLIINOIS. 

THIRD  EDITION. 


TROY,  N.  Y. : 

PUBLISHED  BY  W.  & L.  E.  GURLEY. 


Entered  according  to  Act  of  Congress,  in  the  year  1855^ 

BY  W.  & L.  E,  GURLEY, 

In  the  Clerk’K  Office  of  the  District  Court  for  the  Northern  District  of 
New  York. 


/ 0 > 0 / 3 3,  tk  UtJ  i , tefi 


5^(,,3 


remote 


Q365-yvi3  m UBBARY  OF  THE 


>/? 

-J 


Li^®. 24  1933  I 

***  ILUNOBi 


n? 

n/)^ 


COMPASSES. 


Plain,  with  Jacob  Staff  rnountmgs,  4 inch  needle, , 

(<  ((  ((  U i(  g (<  (( 

“ “ 6 '‘  . 
Vernier,  “ 6 “ “ . 

Rail  Road,  6-^  “ “ 


$20,00 

25.00 

28.00 
35,00 
§5,00 


Compass  Tripod,  with  Cherry  legs,. . . J 5,00 

“ “ lev’g  screws  and  Clamp  and  Tang’t  moTem’t,  12,00 

“ “ “ “ without  “ “ “ “ 10,00 

Compound  Tangent  Ball 4,00 

Brass  Cover  for  compass  glass, 1,00 


TRANSITS. 


Vernier,  plain  telescope  * 6 inch  needle,  with  compass  tripod. 


Surveyors’  “ 

<(  (( 
Engineers’ 


4 

5 “ 

4 “ 

5 “ 


“ adjusting 


with  watch  telescope 
theodolite  axis,. 
**  two  telescopes. 


60,00 


. 100,00 
. 100,00 
. 100,00 
. 120,00 
. 125,00 
. 150,00 
, 150,00 
. 190,00 


. Vertical  circle,  3^  in.  diameter,  vernier  reading  to  five  minutes,  5,00 
“ “ 4i  “ “ “ “ “ single  10,00 

Clamp  and  Tangent  movement  to  axis  of  telescope, 5,00 

Level  on  Telescope,  with  ground  bubble  and  scale, 10,00 

Rack  and  pinion  movement  to  eye  glass, 5,00 

Sights  on  telescope  with  folding  joints, 5,00 

“ “ Standards  at  right  angles  to  telescope, 6,00 


LEVELING  RODS. 


Yankee,  or  Boston, 12,00 

New  York,  with  improved  mountings, 12,00 


* A “ plain  ” tele.scope  is  one  without  any  of  the  attaclimentg,  as  tho  clamp  and 
tangent,  vertical  circle  and  level. 


8466G9 


4 


PEICE  LIST. 


LEVELING  INSTRUMENTS. 


Sixteen  inch  telescope,  with  adjusting  tripod,. $90,00 

Eigliteen  “ “ “ “ “ 90,00 

Twenty  “ “ “ “ “ 90,00 

Twenty-two  “ “ “ ^ “ 90,00 

Farm  level,  “ “ “ “ 45,00 

Builders’  level,  “ “ “ 50,00 


CHAINS. 


100  feet,  with  oval  rings,  No.  5 wire,  iron, 7,50 

“ “ “ “ “ “ 6 “ “ 6,00 

50  “ “ “ “ “ 5 “ “ 4,00 

“ “ “ “ 6 “ “ 3,50 

66  “ round  “ “ 8 “ 3,00 

83  “ “ “ “ 8 “ “ 1,75 

66  “ “ “ “10  “ “ 2,50 

33  “ “ “ “ “10  “ “ 1,50 

66  “ “ “ “ “10  “ steel, 5,00 

33  “ “ “ “10  “ “ ■ 2,75 

Set  11  marking  Pins,.  ,75 

MEASURING  TAPES. 

Chesterman’s  steel,  83  feet, 7,50 

“ 50  “ 11,50 

“ “ 66  “ 14,50 

“ “ 100  “ 20,00 

“ metallic  33  “ 2,50 

“ “ 50  “ 3,00 

“ “ , 60  “ 3,25 

“ “ 66  “ 3,50 

“ “ 70  “ 3,75 

“ “ 80  “ 4,00 

“ “ 100  “ 5,00 


POCKET  COMPASSES. 


With  folding  sights,  2^  inch  needle,  very  serviceable  for  retracing 

lines  once  surveyed, 6,00 

“ “ “ “ “ “ witli  Jacob  staff  mountings, . . 7,50 


“ “ “ 3^  “ “ “ “ “ “ 9,00 

“ “ “ “ “ “ without  “ “ 8,00 

Without  sights,  1 to  2 “ “ from  25  cts.  to  2,50 

Miners’  Coinj)asseH,  for  tracing  iron  ore,.  6,00 


For  |)rice8  of  Drawing  Instruments,  Drawing,  Profile  and  Cross-Section 
Paper;  Colors,  I^encils,  and  a list  of  Standard  Works  on  Surveying  and 
Civil  Jhiginccring,  wo  refer  to  the  Supplement. 


luforraatioit  tu  f Hi'tj}iiscw 


Instruments  Wanted. — In  regard  to  the  best  kind  of  instruments  for 
particular  purposes,  we  would  here  say,  that  where  only  common  survey- 
ing, or  the  bearing  of  lines  in  the  surveys  for  county  maps  is  required,  a 
Plain  Compass  is  all  that  is  necessary.  In  cases  where  the  variation  of 
the  needle  is  to  be  allowed,  as  in  running  over  the  lines  of  an  old  farm,  or 
the  surveys  of  Government  lands,  the  Yernier  Compass,  or  the  Vernier 
Transit,  is  required. 

Where,  in  addition  to  the  variation  of  the  needle,  horizontal  angles  are 
to  be  taken,  in  cases  of  local  attraction,  the  Rail  Road  Compass  is  prefer- 
able ; and  for  a mixed  practice  of  surveying  and  engineering,  we  consider 
the  Surveyors’  Transit  superior  to  any  other  instrument  made  by  us  or 
any  other  manuhicturers. 

Where  Engineering  is  the  exclusive  design,  the  Engineers’  Transit  and 
the  Leveling  Instruments  are  of  course  indispensable. 

The  Farm  and  Builders’  Levels,  are  intended  for  laying  out  mill  seats 
and  determining  the  levels  of  buildings  in  course  of  erection. 

Warranty  — All  our  instruments  are  examined  and  tested  by  us  in  per- 
son, and  are  sent  to  the  purchaser  adjusted  and  ready  for  immediate  use. 

They  are  warranted  correct  in  all  their  parts — we  agreeing  in  the  event 
of  any  defect  appearing  after  reasonable  use,  to  repair  or  replace  with  a 
new  and  perfect  instrument,  promptly  and  at  our  own  cost,  express 
charges  included,  or  we  will  refund  the  money  and  the  express  charges 
paid  by  him. 

Instances  may  sometimes  occur  in  a business  as  large  and  as  widely 
extended  as  ours,  where  owing  to  careless  transportation  or  to  defects 
escaping  the  closest  scrutiny  of  the  maker,  instruments  may  reach  our 
customers  in  bad  condition.  We  consider  the  retention  of  such  instruments 
in  all  cases  an  injury  very  much  greater  to  us  than  to  the  purchaser 
himself. 

Packing,  <fec.— Each  instrument  is  packed  in  a well  finished  mahogany 
case,  furnished  with  lock  and  key  and  brass  hooks,  the  larger  ones  having 
beside  these  a leather  strap  for  convenience  in  carrying.  Each  case  is 
provided  with  screw-drivers,  adjusting  pin,  and  wrench  for  centre  pin,  and 
if  accompanied  with  a tripod,  with  a brass  plumb-bob  ; with  all  instru- 
ments for  taking  angles,  without  the  needle,  a reading  microscope  is  also 
furnished. 


1^ 


6 


INFORMATION  TO  PURCHASERS. 


Unless  tlie  purchaser  is  already  supplied,  each  instrument  is  accompa- 
nied with  our  “ Manual,”  giving  full  instructions  for  such  adjustments  and 
repairs  as  are  possible,  to  one  not  provided  with  the  facilities  of  an  instru- 
ment maker. 

When  sent  to  the  purchaser,  the  mahogany  cases  are  carefully  enclosed 
in  outside  packing  boxes,  of  pine,  made  a little  larger  on  all  sides  to  allow 
the  introduction  of  elastic  material,  and  so  efFecti:ally  are  our  instruments 
protected  by  these  precautions,  that  of  several  thousand  sent  out  by  us 
during  the  last  thirteen  years,  in  all  seasons,  by  every  mode  of  transporta- 
tion, and  to  all  parts  of  the  Union,  and  the  Canadas,  not  more  than  three 
or  four  have  sustained  serious  injury. 

Means  of  Transportation.  — Instruments  can  be  sent  by  Express  to 
almost  every  town  in  the  United  States  and  Canadas,  regular  agents  being 
located  at  all  the  more  important  points,  by  whom  they  are  forwarded  to 
smaller  places  by  stage.  The  charges  of  transportation  from  Troy  to  the 
purchaser  are  in  all  cases  to  be  borne  by  him,  we  guaranteeing  the  safe 
arrival  of  our  instruments  to  the  extent  of  express  transportation,  and 
holding  the  Express  Companies  responsible  to  us  for  all  losses  or  damages 
on  the  way. 

Terms  of  Payment  are  uniformly  cash,  and  we  have  but  one  price. 
Our  prices  for  instruments  are  nearly  one-third  less  than  those  of  other 
makers  of  established  reputation.  They  are  as  low  as  we  think  instru- 
ments of  equal  quality  can  be  made,  and  will  not  be  varied  from  the  list 
given  on  the  previous  pages. 

Remittances  may  be  made  by  a draft,  payable  to  our  order  at  Troy, 
Albany,  New  York,  Boston,  or  Philadelphia,  which  can  be  procured  from 
Banks  or  Bankers  in  almost  all  of  the  larger  villages. 

These  may  be  sent  by  mail  with  the  order  for  the  instrument,  and  if  lost 
or  stolen  on  the  route,  can  be  replaced  by  a duplicate  draft,  obtained  as 
before,  and  without  additional  cost. 

Or  the  customer  may  pay  the  bill  on  receipt  of  the  instrument  to  the 
express  agent,  taking  care  to  send  funds  bankable  in  New  York  or  Boston. 

All  persons  ordering  instruments  by  mail,  or  by  prox^q  may  rely  on 
receiving  as  perfect  and  cheaply  ns  if  ordered  in  person. 

W.  & L.  E.  GUllLEY, 

Mathematical  Instniment  Mahers^ 

Fulton  St.,  oitosite  Union  R.  R.  Depot,  Troy,  N.  Y. 


PREFACE. 


In  offering  this  little  work  to  the  public,  the  publishers  have  designed 
to  supply  a want  which  an  experience  of  many  years  in  the  manufacture 
of  Instruments,  as  well  as  practice  in  the  field,  has  taught  them,  is  very 
generally  felt  by  American  Surveyors  and  Engineers. 

The  various  Instruments  employed  in  English  and  European  practice 
are  so  different  from  those  preferred  by  the  great  majority  of  American 
Engineers,  that  no  description  of  the  former,  however  excellent,  is  applicar 
ble  to  such  as  are  manufactured  aud  used  in  our  own  country. 

The  entire  Absence  of  any  treatise  upon  American  Instruments,  as  well 
as  the  numerous  enquiries  which  are  made  by  our  business  correspondents, 
has  led  us  to  believe  that  a Manual,  furnishing  a full  description  of  the 
peculiarities  and  adjustments  of  those  manufactured  at  our  establishment, 
would  be  acceptable,  not  only  to  our  own  customers,  but  to  the  profession 
generally. 

With  the  hope,  therefore,  that  our  little  book  may  enable  the  Engineer 
and  Surveyor  to  understand  their  instruments,  and  discover  and  rectify 
any  derangement  in  their  adjustments,  or  injury  from  ordinary  accidents, 
we  now  commit  it  to  the  indulgence  of  those  for  whom  it  has  been 
designed. 

W.  & L.  E.  GURLEY. 

Troy,  May  1,  1857. 


SURVEYING  INSTRUMENTS. 


The  various  instruments  used  in  Surveying  may  be  conve- 
niently arranged,  into  two  general  divisions. 

(1.)  Needle  instruments,— or  suck  as  owe  tlieir  accuracy  and 
value  to  the  magnetic  needle  only,  embracing  the  Plain  and  Ver- 
nier Compasses,  and  the  Vernier  Transit. 

(2.)  Angular  instruments,  including  those  in  which  the  hori- 
zontal angles,  are  measured  by  a divided  circle  and  verniers,  as 
well  as  by  the  needle  also  ; as  the  Rail  Road  Compass,  the  Sur- 
veyors’ and  Engineers’  Transits,  &c. 

In  the  present  work  we  shall  consider  first,  those  instruments 
comprised  in  the  first  division,  and,  as  in  these  the  accuracy  of 
the  horizontal  angles  indicated,  depends  upon  the  delicacy  of  the 
needle,  and  the  constancy  with  which  it  assumes  a certain  direc- 
tion, termed  the  “ magnetic  meridian,  ” we  shall  here  remark 
briefly  upon,  the  /orm,  the  length  and  the  movement  of 

The  Magnetic  Needle. — The  forms  of  the  needle  are  almost 
infinitely  varied,  according  to  the  taste  or  fancy  of  the  maker  or 
surveyor,  but  may  be  resolved  into  two  general  classes,  one  having 
the  greatest  breadth  in  a horizontal,  the  other  in  a vertical 
direction. 

V^e  have  usually  made  our  needles  about  one  twentieth*  of  an 
inch  broad  and  one  third  as  thick,  parallel  from  end  to  end,  the 
north  and  south  poles  being  distinguished  from  each  other,  by  a 
small  scollop  on  the  north  end. 

The  length  of  the  needle  varies  in  different  instruments,  from 
four  to  six  or  even  seven  inches,  those  of  five  and  a half,  or  six 
inches  long,  being  generally  preferred  by  surveyors. 


10 


THE  PLAIN  COMPASS. 


The  movement  of  the  needle,  with  the  least  possible  friction,  is 
eecured  by  suspending  it,  by  a jeweled  centre  upon  a hardened 
steel  pivot,  the  point  of  which  is  made  perfectly  sharp  and 
smooth. 

The  test  of  the  delicacy  of  a magnetic  needle  is  the  number  of 
horizontal  vibrations,  which  it  will  make  in  a certain  arc,  before 
coming  to  rest — besides  this,  most  surveyors  prefer  also  to  see  a 
sort  of  quivering  motion  in  a vertical  direction. 

This  quality  which  is  manifested  more  in  a horizontal,  than  in 
a vertical  needle  and  depends  upon  the  near  coincidence  of  the  point 
of  suspension,  with  the  centre  of  gravity  of  the  needle,  serves  to 
show  merely,  that  the  cap  below  is  unobstructed. 

Having  now  considered  the  different  qualities  of  a good  needle, 
we  shall  proceed  to  speak  of  those  instruments  of  which  it  makes 
so  important  a part ; of  these  the  most  simple  is  that  termed  the 

PLAIN  COMPASS. 

Fig.  1. 


THE  PLATH  COMPASS. 


11 


inches  long,  a graduated  circle,  main  plate,  levels,  and  sights, 
and  is  placed  upon  the  brass  head  of  the  Jacob  staff.” 

The  Compass  Circle,  in  this,  as  in  all  our  instruments,  is 
divided  to  half  degrees  on  its  upper  surface,  the  whole  degree 
marks  being  also  cut  down  on  the  inside  circumference,  and  is  fig- 
ured from  0 to  90,  on  each  side  of  the  centre  or  “line  of  zeros.” 

The  circle  and  face  of  the  compass  are  silvered. 

The  Spirit  Levels  are  placed  at  right  angles  to  each  other 
so  as  to  level  the  plate  in  all  directions,  and  are  balanced,  upon  a 
pivot  underneath  the  middle  of  the  tube,  so  as  to  be  adjustable  bj 
a common  screw-driver. 

The  Sights,  or  standards,  have  fine  slits  eut  through  nearlj 
their  whole  length,  terminated  at  intervals  by  large  circular  aper- 
tures, through  w^hich  the  object  sighted  upon  is  more  readily 
found.  Sometimes  a fine  horse-hair  or  wire  is  substituted  for  one 
half  the  slote,  and  placed  alternately  with  it  on  opposite  sights. 

Tangent  Scale. — The  right  and  left  hand  edges  of  the  sights 
of  our  compasses,  have  respectively  an  eye-piece,  and  a series,  of 
divisions,  by  which  angles  of  elevation  and  depression,  for  a range 
of  about  twenty  degrees  each  way,  can  be  taken  with  considerable 
accuracy. 

Such  an  arrangement  is  very  properly  termed  a “ tangent 
scale,”  the  divided  edges  of  the  north  si'ght,  being  tangents  to 
segments'  of  circles  having  their  centres  at  the  eye-pieces,  and 
their  points  of  contact  with  the  tangent  lines  at  the  zero  divisions 
of  the  scale. 

The  cut  shows  the  eye-piece  and  divisions  for  angles  of  de- 
pression ; those  for  angles  of  elevation,  concealed  in  this  cut,  are 
seen  in  that  of  the  Railroad  Compass. 

The  Jacob  Staff  mountings  which  are  furnished  with  all  our 
compasses,  and  packed  in  the  same  case,  consist  of  the  brass  head 
already  mentioned,  and  an  iron  ferule  or  shoe  pointed  with  steel 
so  as  to  be  set  firmly  in  the  ground. 


12 


THE  PLAIN  COMPASS. 


The  staff  to  which  the  mountings  should  be  well  fitted  and 
driven  on,  is  procured  from  anj  wheelright,  or  selected  by  the  sur- 
veyor himself,  from  a sapling  of  the  forest. 


To  adjust  the  Compass. 

The  Levels. — First  bring  the  bubbles  into  the  centre,  by  the 
pressure  of  the  hand  on  different  parts  of  the  plate,  and  then  turn 
the  compass  half  way  around  ; should  the  bubbles  run  to  the  end 
of  the  tubes,  it  would  indicate  that  those  ends  were  the  highest  ; 
lower  them  by  tightening  the  screws  immediately  under,  and 
loosening  those  under  the  lowest  ends  until  by  estimation  the  error 
is  half  removed;  level  the  plate  again,  and  repeat  the  first  opera- 
tion, until  the  bubbles  will  remain  in  the  centre,  during  an  entire 
revolution  of  the  compass. 

The  Sights  may  next  be  tested  by  observing,  through  the 
slits,  a fine  hair  or  thread  made  exactly  vertical  by  a plumb. 
Should  the  hair  appear  on  one  side  of  the  slit  the  sight  must  be 
adjusted  by  filing  off  its  under  surface  on  that  side  which  seems 
the  highest. 

The  Needle  is  adjusted  in  the  following  manner  : — Having  the 
eye  nearly  in  the  same  plane  with  the  graduated  rim  of  the  com- 
pass circle,  with  a small  -splinter  of  wood,  or  a slender  iron  wire, 
bring  one  end  of  the  needle  in  line  with  any  prominent  division 
of  the  circle,  as  the  zero,  or  ninety  degree  mark,  and  notice  if  the 
other  end  corresponds  with  the  degree  on  tbe  opposite  side ; if  it 
does,  the  needle  is  said  to  “ cut’’  opposite  degrees ; if  not,  bend 
the  centre-pin  by  applying  a small  brass  wrench,  furnished  with 
our  compasses,  about  one-eiglith  of  an  incli  below  the  point  of  the 
pin,  until  the  ends  of  tlie  needle  are  brouglit  into  line  with  the 
opposite  degrees. 

Then  holding  the  needle  in  tlie  same  position,  turn  the  compass 
half  way  around,  and  note  wliether  it  now  cuts  opposite  degrees. 


THE  PLAIN  COMPASS. 


13 


If  not,  correct  half  the  error,  by  bending  the  needle,  and  the 
remainder  by  bending  the  centre-pin. 

The  operation  should  be  repeated  until  perfect  reversion  is 
secured  in  the  first  position. 

This  being  obtained,  it  may  be  tried  on  another  quarter  of  the 
circle ; if  any  error  is  there  manifested,  the  correction  must  be 
made  in  the  centre  pin  only,  the  needle  being  already  straightened 
by  the  previous  operation. 

When  again  made  to  cut,  it  should  be  tried  on  the  other  quar- 
ters of  the  circle,  and  corrections  made  in  the  same  manner  until 
the  error  is  entirely  removed,  and  the  needle  will  reverse  in  every 
point  of  the  divided  surface. 

To  use  the  Compass, 

In  using  the  Compass  the  Surveyor  should  keep  the  south  end 
towards  his  person,  and  read  the  bearings  from  the  north  end  of 
the  needle.  He  will  observe  that  the  E and  W letters  on  the 
face  of  the  compass  are  reversed  from  their  natural  position,  in 
order  that  the  direction  of  the  line  of  sight  may  be  correctly  read. 

The  compass  circle  being  graduated  to  half  degrees,  a little 
practice  will  enable  the  surveyor  to  read  the  bearings  to  quar- 
ters, or  even  finer — estimating  with  his  eye  the  space  bisected  by 
the  point  of  the  -needle,  and  as  this  is  as  low  as  the  Traverse 
table  is  usually  calculated,  it  is  the  general  practice. 

Sometimes,  however,  a small  vernier  is  placed  upon  the  south 
end  of  the  needle,  and  reads  the  circle  to  five  minutes  of  a degree 
— the  circle  being  in  that  case  graduated  to  whole  degrees. 

Tliis  contrivance,  however,  is  quite  objectionable  on  account 
of  the  additional  weight  imposed  on  the  centre-pin,  and  the  diffi- 
culty of  reading  a vernier  which  is  in  constant  vibration,  and  is 
therefore  but  little  used. 

To  Take  Angles  of  Elevation. — Having  first  leveled  the 
compass,  bring  the  south  end  towards  you,  and  place  the  eye  at 
2 


14 


THE  PLAIN  COMPASS. 


the  little  button,  or  eye  piece,  on  the  right  side  of  the  south  sight, 
and  with  the  hand  fix  a card  on  the  front  surface  of  the  north 
sight,  so  that  its  top  edge  will  be  at  right  angles  to  the  divided 
edge,  and  coincide  with  the  zero  mark ; then  sighting  over  the  top 
of  the  card,  note  upon  a flagstaff  the  height  cut  by  the  line  of 
sight;  then  move  the  staff  up  the  elevation,  and  carry  the  card 
along  the  sight  until  the  line  of  sight  again  cuts  the  same  height 
on  the  staff,  read  off  the  degrees  and  half  degrees  passed  over  by 
the  card,  and  we  shall  have  the  angle  required. 

For  Angles  of  Depression. — Proceed  in  the  same  manner, 
using  the  eye-piece  and  divisions  on  the  opposite  sides  of  the 
sights,  and  reading  from  the  top  of  the  standards. 

Jacob  Staff  Socket. — The  compass  is  furnished  with  a ball 
spindle,  or  socket,  upon  which  it  turns,  and  by  which  it  is  leveled. 
Tlie  ball  may  be  placed  in  a single  or  “Jacob  staff”  socket,  as 
represented  in  the  figure,  or  in  a compass  tripod,  such  as  is  shown 
in  the  cut  of  the  Vernier  Transit  beyond. 

Clamp  Screw. — In  the  side  of  the  hollow  cylinder,  or  socket,  of 
the  compass  which  fits  to  the  ball  spindle,  is  a screw  by  which 
the  instrument  may  be  clamped  to  the  spindle  in  any  position. 

Spring  Catch. — Besides  the  clamp  screw,  we  have  recently  fit- 
ted to  the  sockets  of  our  compasses  a little  spring  catch,  which,  as 
soon  as  the  instrument  is  set  upon  the  spindle,  slips  into  a groove  and 
thus  removes  all  danger  of  falling  when  the  instrument  is  carried. 

Needle  Lifter. — There  is  also,  underneath  the  main  plate,  a 
needle  lifting  screw  which,  by  moving  a concealed  spring,  raises 
the  needle  from  the  pivot,  and  thus  prevents  the  blunting  of  the 
point  in  transportation. 

When  the  compass  is  not  in  use  it  is  the  practice  of  many 
surveyors  to  let  down  the  needle  upon  the  point  of  the  centre-pin, 
and  let  it  assume  its  position  in  the  magnetic  meridian  so  as  to 
relain  or  (*ven  increase  its  polarity. 

We  would  advise  in  addition,  that  after  the  needle  has  settled 


THE  PLAIN  COMPASS. 


15 


it  should  be  raised  against  the  glass,  in  order  not  to  dull  the  point 
of  suspension. 

Electricity. — A little  caution  is  necessary  in  handling  the  com- 
pass, that  the  glass  covering  be  not  excited  by  the  friction  of  cloth, 
silk,  or  tlie  hand,  so  as  to  attract  the  needle  to  its  under  surface. 

A brass  cover  is  sometimes  fitted  over  the  glass  as  a precaution 
against  disturbances  of  this  kind. 

When,  however,  the  glass  becomes  electric,  the  fluid  may  be 
removed  by  breatliing  upon  it,  or  touching  different  points  of  its 
surface  with  the  moistened  finger. 

An  ignorance  of  this  apparently  trifling  matter  has  . caused 
many  errors  and  perplexities  in  the  practice  of  the  inexperienced 
surveyor. 

Repairs  of  the  Compass^ 

To  ena.ble  the  Surveyor  to  make  such  repairs  as  are  possible 
without  having  recourse  to  an  instrument  maker,  we  here  add  a 
few  simple  directions. 

1.  The  Needle. — It  may  sometimes  happen  that  the  needle 
has  lost  its  polarity,  and  needs  to  be  re-magnetized ; this  is  effected 
in  the  following  manner  : 

The  operator  being  provided  with  an  ordinary  permanent  mag- 
net,^ and  holding  it  before  him,  should  pass  with  a gentle  pressure 
each  end  of  the  needle  from  centre  to  extremity  over  the  magnetic 
pole,  describing  before  each  pass  a circle  of  about  six  inches 
radius,  to  which  the  surface  of  the  pole  is  tangent,  drawing  the 
needle  towards  him,  and  taking  care  that  the  north  and  south 
ends  are  applied  to  the  opposite  poles  of  the  magnet. 

Should  the  needle  be  returned  in  a path  near  the  magnetic 
pole,  the  current  induced  by  the  contact  of  the  needle  and  mag- 
net in  the  pass  above  described,  would  be  reversed,  and  thus  the 
magnetic  virtue  almost  entirely  neutralized  at  each  operation. 

When  the  needle  has  been  passed  about  twenty-five  times  in 


♦ A mag^net  suitable  for  this  purpose  costs  from  12  to  25  cents. 


16 


THE  PLAIN  COMPASS. 


succession,  in  the  manner  just  described,  it  may  be  considered 
as  fully  charged. 

A fine  brass  wire  is  wound  in  two  or  three  coils  on  the  south 
end  of  the  needle,  and  may  be  moved  back  or  forth,  in  order  to 
counterpoise  the  varying  weight  of  the  north  end. 

2.  The  Centre-Pin. — This  should  occasionally  be  examined, 
and  if  much  dulled,  taken  out  with  the  brass  wrench,  already 
spoken  of,  or  with  a pair  of  plyers,  and  sharpened  on  a hard  oil 
stone — the  operator  placing  it  in  the  end  of  a small  stem  of  wood, 
or  a pin  vice,  and  delicately  twirling  it  with  the  fingers  as  he  moves 
it  back  and  forth  at  an  angle  of  about  45®  to  the  surface  of  the 
stone. 

When  the  point  is  thus  made  so  fine  and  sharp  as  to  be  invisi- 
ble to  the  eye,  it  should  be  smoothed  by  rubbing  it  on  the  surface 
of  a soft  and  clean  piece  of  leather. 

3.  To  PUT  IN  A New  Gla.ss. — Unscrew  the  “ bezzel  ring’* 
which  holds  it,  take  out  the  little  brass  ring  and  the  old  glass,  and 
scrape  out  the  putty ; then  if  the  new  glass  does  not  fit,  smooth  off 
its  edges  by  holding  it  obliquely  on  the  surface  of  a grind-stone 
until  it  will  enter  the  ring  easily ; then  put  in  new  putty,  spring 
in  the  brass  ring,  and  the  operation  will  be  completed. 

4.  To  REPLACE  A SPIRIT  Level. — Take  out  the  screws  which 
hold  it  on  the  plate,  pull  off  the  brass  ends  of  the  tube,  and  with 
a knife-blade  scrape  out  the  plaster  from  the  tube ; then  with 
a stick,  made  a little  smaller  than  the  diameter  of  the  tube,  and 
with  its  end  hollowed  out,  so  that  it  will  bear  only  on  the  broad 
surface  of  the  level  vial,  push  out  the  old  vial,  and  replace  it 
with  a new  one,  taking  care  that  the  crowning  side,  which  is 
usually  marked  with  a file  on  tlie  end  of  the  vial,  is  placed  on  the 
upper  side. 

When  tlie  vial  does  not  fit  the  tulie  it  must  be  wedged  up  by 
putting  under  little  slips  of  paper  until  it  moves  in  snugly. 

After  the  vial  is  in  its  place,  put  around  its  end  a little  boiled 


THE  PLAIN  COMPASS. 


17 


plaster,  mixed  with  water  to  the  consistency  of  putty,  taking  care 
not  to  allow  any  to  cover  the  little  tip  of  the  glass,  then  slip  in 
the  brass  ends,  and  the  operation  will  be  completed, 

A little  beeswax,  melted  and  dropped  upon  the  ends  of  the  vial 
is  equally  as  good  as  the  boiled  plaster,  and  often  more  easily 
obtained. 

We  would  here  remark  that  an  extra  glass  and  level  vials  are 
always  furnished,  free  of  charge,  with  our  instruments,  whenever 
desired  by  the  purchaser,  • 

Sizes  of  the  Plain  Compass. 

Three  different  sizes  of  this  instrument  are  in  common  use — 
having  respectively  four,  five,  and  six  inch  needles,  and  differing 
also  in  the  length  of  the  main  plate,  which  in  the  four  inch  Com> 
pass  is  twelve  and  a half  inches  long,  and  in  the  larger  sizes 
fifteen  and  a half  inches. 

The  six  inch  needle  compass  is  generally  preferred. 

Weight  of  the  Plain  Compasses. 

The  average  weights  of  the  different  sizes,  with  the  brass 
mountings  of  the  Jacob  Staf^  are. 

For  the  4 inch  needle,  6 lbs. 

For  the  5 inch  needle,  7-^  lbs. 

For  the  6 inch  needle,  8|-  lbs. 

The  Plain  Compass,  which  was  the  only  one  in  use  in  this 
country  previous  to  the  time  of  David  Rittenhouse,  lias  gradually 
given  way  to  the  superior  advantages  of  the  Vernier  or  Rittenliouse 
Compass,  which  we  shall  now  proceed  to  describe.. 

2^ 


SURVEYING  INSTRUMENTS. 

1 


THE  VERNIER  COMPASS. 

Fig.  2 


The  Vernier  Compass,  represented  in  fig.  2 differs  from  the 
instrument  just  described,  in  having  its  compass  circle  with  a 
vernier  attached,  movable  about  a common  centre,  bj  turning  the 
“ tangent  screw,’’  seen  at  the  south  end  of  the  plate. 

The  superiority  of  the  Vernier  over  the  Plain  Compass  consists 
in  its  adaptation  to  the  retracing  the  lines  of  an  old  survey,  and 
in  the  surveys  of  the  U.  S.  public  lands,  where  the  lines  are  based 
on  a true  meridian. 

Variation  of  the  Needle. 

Jt  is  well  known  that  the  magnetic  needle,  in  almost  all  parts 


THE  VERNIER  COMPASS.  19 

of  the  United  States,  points  more  or  less  to  the  east  or  west  of 
a true  meridian,  or  north  and  south  line. 

This  deviation,  which  is  called  the  Variation  of  Declination 
of  the  needle,  is  not  constant,  but  increases  or  decreases  to  a very 
sensible  amount  in  a series  of  jears^ 

Thus  at  Troy,  N,  Y.^  a line  bearing  in  1830,  N.  3U  E.  would 
now,  1857,  with  the  same  needle,  have  a bearing  of  about  N.  32^ 
E.,  the  needle  having  thus  in  that  interval,  travelled  a full  degree 
to  the  west. 

For  this  reason,  therefore,  in  running  over  the  lines  of  a farm 
from  field  notes  of  some  years  standing,  the  Surveyor  would  be 
obliged  to  make  an  allowance,  both  perplexing  and  uncertain,  in 
the  bearing  of  every  line. 

To  avoid  this  difficulty  the  vernier  was  devised,  the  arrange- 
ment of  which  we  sliall  now  describe. 

The  Vernier  is  divided  on  its  edge  to  thirty  equal  parts,  and 
figured  in  two  series  on  each  side  of  the  centre. 

In  the  same  plane  with  the  vernier  is  an  arc  or  limb,  fixed  to 
the  main  plate  of  the  compass,  and  graduated  to  half  degrees. 

The  surfaces  of  both  vernier  and  limb  are  silvered. 

On  the  vernier  are  thirty  equal  divisions,  which  exactly  corres- 
pond in  length  with  thirty-one  of  the  half  degrees  of  the  limb. 

Each  division  of  the  vernier,  is  therefore,  one-thirtieth,  or,  in 
otliei"  words,  one  minute  longer  than  a single  division  of  the  limb. 

To  Head  the  Vernier. — In  ^Yeading”  the  vernier,  if  it  is 
moved  to  the  riglit,  count  the  minutes  from  its  zero  point  to  the 
left,  and  vice  versa.  Proceed  thus  until  a division  on  the  vernier 
is  found  exactly  in  line  with  anotlier  on  the  limb,  and  tlie  lower 
row  of  figures  on  the  vernier  will  give  the  number  of  minutes 
passed  over.  When  the  vernier  is  moved  more  than  fifteen  min- 
utes to  either  side,  tlie  number  of  the  additional  minutes  up  to 
thirty  or  one-half  degree  of  the  limb  is  given  by  the  upper  row  of 
figures  on  the  opposite  side  of  the  vernier. 


20 


TH£1  VERNlEH  OOMPASS. 


To  read  beyond  thirty,  add  the  minutes  given  by  the  vernier 
to  that  number,  and  the  sum  will  be  the  correct  reading. 

In  all  cases  when  the  zero  point  of  the  vernier  passes  a whole 
degree  of  the  limb,  this  must  be  added  to  the  minutes,  in  order  to 
define  the  distance  over  which  the  vernier  has  been  moved. 

To  Turn  off  the  Variation. — It  will  now  be  seen,  that  the 
Surveyor  having  the  Vernier  Compass-,  can  by  moving  the  vernier 
to  either  side,  and  with  it  of  course  the  compass  circle  attached,  set 
the  compass  to  any  variation. 

He  therefore  places  his  instrument  on  some  well  defined  line  of 
the  old  survey,  and  turns  the  tangent  screw  until  the  needle  of  his 
compass  indicates  the  same  bearing  as  that  given  in  the  old  field 
notes  of  the  original  survey. 

Then  screwing  up  the  clamp  screw  underneath  the  vernier,  he 
can  run  all  the  other  lines  from  the  old  field  notes  without  further 
alterationv 

The  reading  of  the  vernier  on  the  limb  in  such  a case,  would 
give  the  change  of  variation  at  the’ two  different  periods. 

The  variation  of  the  needle  at  any  place  being  known,  a true 
meridian,  or  north  and  south  line,  may  be  run  T)y  moving  the 
vernier  U)  either  side,  as  the  variation  is  east  or  west,  until  the 
arc  passed  over  on  the  limb  is  equal  to  the  angle  of  variation ; and 
then  turning  the  compass  until  tlie  needle  is  made  to  cut  the  zeros 
on  the  divided  circle,  when  the  line  of  the  sights  would  give  the 
direction  of  the  true  meridian  of  the  place. 

Such  a change  in  flie  position  of  the  vernier  is  always  necessary 
in  surveying  U.  S.  puldic  lands,  which  are  always  run  from  the 
true  meridian. 

“ 'JhiE  LINE  OF  NO  VAiMATiON, as  it  is  Called,  or  that  upon 
wliicli  the  needle  will  indicate  a true  nortli  and  south  direction,  is 
situated  in  tlie  United  States,  nearly  in  an  imaginary  line  drawn 
from  the  middle  of  lake  Erie  to  cape  llatteras,  on  the  coast  of 
North  Carolina. 

A Compass  needle,  tlieridbre,  placed  cast  of  this  line,  would 


THE  VERNIER  COMPASS. 


21 


have  a variation  to  the  west,  and  when  placed  west  of  the  line, 
the  variation  would  be  to  the  east,  and  in  both  cases  the  varia- 
tion would  increase  as  the  needle  was  carried  farther  from  the 
line  of  no  variation. 

Thus  in  Minnesota  the  variation  is  from  15^  to  16®  to  the  east, 
while  in  Maine  it  is  from  17^  to  18°  to  the  west. 

At  Troy,  in  the  present  year,  1857,  the  variation  is  about  7® 
47'  to  the  w^est,  and  is  increasing  in  the  same  direction  from  two 
to  three  minutes  annually. 

To  Kead  to  Minutes. — A less  important  use  of  the  vernier 
is  to  give  a reading  of  the  needle  to  single  minutes,  wdiich  is 
obtained  as  follow^s : 

First  be  sure,  as  in  all  observations,  that  the  zero  of  the  ver- 
nier exactly  corresponds  wdth  that  of  the  limb  ; then  noting  the 
number  of  whole  degrees  given  by  the  needle,  move  back  the 
compass  circle  with  the  tangent  screw  until  the  nearest  wdiole 
degree  mark  is  made  to  coincide  with  the  point  of  the  needle, 
read  the  vernier  as  before  described,  and  this  reading,  added  to 
the  whole  degrees,  will  give  the  bearing  to  minutes. 

To  Use  the  Vernier  Compass. 

Proceed  in  the  same  manner  as  directed  in  regard  to  the  Plain 
Compass,  when  making  new  surveys,  always  taking  care  that 
the  vernier  is  set  at  zero  and  securely  clamped  by  screwing  up 
the  nut  beneath  the  plate. 

In  surveying  old  farms,  allowance  and  correction  must  be  made 
for  the  variation,  as  just  described. 

Sizes  of  the  Vernier  Compass. 

We  make  but  one  size  of  this  instrument,  having  a six  inch 
needle  and  a main  plate  fifteen  and  a half  inches  long. 

Weight  of  the  Vernier  Compass. 

The  average  weight  of  this  instrument,  with  the  Jacob  staff 
mountings,  is  about  9^  pounds. 

The  adjustments  of  the  Vernier  Compass  are  mainly  those 
of  the  instrument  first  described,  and  need  not  here  be  repeated. 


SURVEYING  INSTRUMENTS 


THE  VERNIER  TRANSIT. 
Fig.  3. 


The  Vernier  Transit,  or  Transit  Compass,  represented  in  the 
cut  above,  has  the  same  general  properties  as  tlie  Vernier  Com- 
pass, but  is  furnished  willi  a telescope  in  place  of  the  ordinary 
sights. 


THE  VERNIER  TRANSIT. 


The  telescope  is  from  ten  to  twelve  inches 
long,  and  sufficiently  powerful  to  see  and  set 
a flag  at  a distance  of  two  miles,  in  a clear 
day. 

The  cross-bar  in  which  it  is  fixed,  turns 
readily  in  the  standards,  so  that  the  telescope 
can  be  turned  in  either  direction,  and  back 
and  fore  sights  be  taken  without  removing 
the  instrument. 

Like  all  telescopes  used  by  us  in  our  in- 
struments, it  shows  objects  in  an  erect  po- 
sition. 

The  Telescope. — The  interior  construc- 
tion of  tlie  telescope  of  the  Vernier  Transit 
which  is  very  similar  to  those  of  the  other 
instruments  we  shall  describe,  is  well  shown 
in  the  longitudinal  section  represented  in 
fig.  4. 

As  here  seen,  the  telescope  consists  essen- 
tially of  an  object-glass,  an  eye-piece  tube, 
and  a cross-wire  ring,  or  diaphragm. 

The  object-glass  is  composed  of  two  lens- 
es, one  of  flint,  the  other  of  crown  glass, 
which  are  so  made  and  disposed,  as  to  show 
the  object  seen  through  it  without  color  or 
distortion. 

The  object-glass,  and  the  whole  telescope 
is  therefore  said  to  be  “ achromatic.” 

The  eye-piece  is  made  up  of  four  plano- 
convex lenses,  which,  beginning  at  the  eye 
end,  and  proceeding  on,  are  called  respect- 
ively, the  eye,  the  field,  the  amplifying,  and 
the  object  lenses. 


24 


THE  VERNIER  TRANSIT. 


Together,  they  form  a compound  microscope,  magnifying  the 
minute  image  ol  any  object  formed  at  the  cross-wires  by  the 
interposition  of  the  object-glass. 


Fig.  5. 


The  Cross- Wikes. — The  cross-wire  diaphragm,  two  views  of 
which  are  here  exhibited,  is  a small  ring  of  brass,  suspended  in 
the  tube  of  the  telescope  by  four  capstan  head  screws,  which 
press  upon  the  washers  shown  on  the  outside  of  the  tube. 

The  ring  can  thus  be  moved  in  either  direction,  by  working 
the  screws  with  an  ordinary  adjusting  pin. 

Across  the  flat  surface  of  the  ring  two  fine  fibres  of  spider’s 
web  are  extended  at  right  angles  to  each  other,  their  enhs  being 
cemented  with  beesw^ax,  or  varnish,  into  fine  lines  cut  in  tlie  metal 
of  the  ring. 

The  intersection  of  the  wires  forms  a very  minute  point,  which, 
when  they  are  adjusted,  determines  tlie  optical  axis  of  the  tele- 
scope, and  enaldes  the  Surveyor  to  fix  it  upon  an  object  witli  the 
greatest  precision. 

The  imaginary  line  passing  tlirough  the  optical  axis  of  the 
telescope,  is  termed  tlie  “line  of  collimation,”  and  the  operation 
of  bringing  llie  intersection  of  the  wires  into  the  optical  axis,  is 


THE  VERNIER  TRANSIT. 


25 


called  the  ‘‘adjustment  of  the  line  of  collimation.’^  This  will  be 
hereafter  described. 

The  openings  in  the  telescope  tube  are  made  considerably 
larger  than  the  screws,  so  that  when  these  are  loosened,  the 
whole  ring  can  be  turned  around  for  a short  distance  in  either 
direction. 

The  object  of  this  will  be  seen  more  plainly,  when  we  describe 
the  means  by  which  the  wire  is  made  truly  vertical. 

The  sectional  view  of  the  telescope  (fig  4,)  also  shows  two 
moveable  rings,  one  placed  at  A A,  the  other  at  C 0,  which  are 
respectively  used,  to  effect  the  centering  of  the  eye-piece,  and  the 
adjustment  of  the  object-glass  slide. 

Tlie  centering  of  the  eye-tube  is  performed  after  the  wires  have 
been  adjusted,  and  is  effected  by  moving  the  ring,  by  means  of 
the  screws,  shown  on  the  outside  of  the  tube,  until  the  intersection 
of  the  wires  is  brouglit  into  the  centre  of  the  field  of  view. 

The  adjustment  of  the  object  slide,  which  will  be  fully  described 
in  our  account  of  the  Leveling  Instrument,  secures  the  movement 
of  the  object-glass  in  a straigljt  line,  and  thus  keeps  the  line  of 
collimation  in  adjustment  through  the  wliole  range  of  the  slide, 
preventing  at  the  same  time  what  is  termed  the  “ travelling  ” of 
the  wires. 

Tlfs  adjustment  which  is  peculiar  to  our-  telescopes,  is  always 
made  in  the  process  of  construction,  and  needing  no  further  atten- 
tion at  the  hands  of  the  Engineer,  is  concealed  within  the  hollow 
ball  of  the  telescope  axis. 

Optical  Principles  of  the  Telescope, 

In  order  that  the  advantages  gained  by  the  use  of  the  tele- 
scope may  be  more  fully  understood,  we  shall  here  venture  briefly 
to  consider  the  optical  principles  involved  in  its  construction. 

We  are  said  to  “see’’  objects  because  the  rays  of  light  which 
proceed  from  all  their  parts,  after  passing  through  the  pupil  of  the 
eye,  are  by  the  crystalline  lens  and  vitreous  humor,  converged 
3 


26 


THE  VERNIER  TRANSIT. 


to  a focus  on  tlie  retina,  where  they  form  a very  minute  inverted 
image  ; an  impression  of  which  is  conveyed  to  the  brain  by  the 
optic  nerve. 

The  rays  proceeding  from  the  extremities  of  an  object,  and 
crossing  at  the  optic  centre  of  the  eye,  form  the  “visual  angle,’^ 
or  that  under  which  the  object  is  seen. 

The  apparent  magnitude  of  objects  depends  on  the  size  of  the 
visual  angle  which  they  subtend,  and  this  being  great  or  small, 
as  the  object  is  near  or  distant — the  objects  will  appear  large  or 
small,  in  an  inverse  proportion  to  the  distances  which  separate 
them  from  the  observer. 

Thus,  (in  fig.  6,)  if 
the  distance  0 A is  one- 
half  of  0 B,  the  visual 
S angle,  subtended  by  the 
object  at  the  point  A, 
and  therefore  the  appa- 
rent magnitude  of  the 
object  will  be  twice  that  observed  at  B.  If,  therefore,  the  visual 
angle  subtended  by  any  object,  can  be  made  by  any  means  twice 
as  large,  the  same  effect  will  be  produced  as  if  the  observer  w^ere 
moved  up  over  one-half  the  intervening  distance. 

Now  this  is  the  principal  advantage  gained  in  the  use  of  a 
telescope. 

The  object-glass  receiving  the  rays  of  light  which  proceed  from 
all  the  points  of  a visible  object,  converges  them  to  a focus  at  the 
cross- wires,  and  there  forms  a minute,  inverted,  and  very  bright 
image,  which  may  be  seen  by  placing  a piece  of  ground  glass  to 
receive  it  at  that  point. 

The  eye-piece  actinf?  as  a compound  microscope,  magnifies  this 
image,  restores  it  to  its  natural  position,  and  conveys  it  to  the  eye, 

I'lie  visual  angle  which  the  image  there  subtends,  is  as  many 
times  greater  than  that  which  would  be  formed  without  the  use  of 
the  telescope,  as  the  number  which  expresses  its  magnifying  power. 


THE  VERNIER  TRANSIT. 


27 


Thus,  a telescope  which  magnifies  twenty  times, 
increases  the  visual  angle  just  as  much,  and  there- 
fore diminishes  the  apparent  distance  of  the  object 
twenty  times — or  in  other  words,  it  will  show  an 
object  two  hundred  feet  distant,  with  the  same 
distinctness,  as  if  it  was  distant  only  ten  feet  from 
the  naked  eye. 

The  accompanying  cut,  (fig.  7,)  which  we  are 
kindly  permitted*  to  copy  from  an  excellent  treatise 
on  surveying,  by  Prof.  Gillespie  of  Union  College, 
will  give  a correct  idea  of  the  manner  in  which 
the  rays  of  light  coming  from  an  object  are  affect- 
ed, by  passing  through  the  several  glasses  of  a 
telescope. 

We  shall  only  consider  the  rays  which  proceed 
from  the  extremities;  these,  after  passing  through 
the  object-glass,  here  shown  as  a single  lens,  are 
conveyed  to  the  point  B,  the  centre  of  tlie  cross- 
wires and  the  common  focus  of  the  object  and  eye 
glasses.  At  this  place  the  rays  cross  each  other 
and  the  image  is  inverted. 

The  rays  next  come  to  the  object  lens  C,  and 
passing  through  it  are  refracted  so  as  again  to 
cross  each  other,  and  come  thus  to  the  amplifying 
lens  D.  By  this  they  are  again  refracted,  made 
more  nearly  parallel  and  thus  reach  the  large  field 
lens  E.  After  passing  through  this,  they  form  a 
magnified  and  erect  image  in  the  focus  of  the  eye 
lens  G.  By  the  eye  lens  the  image  is  still  further 
magnified,  and  at  last  enters  the  eye  of  the  ob- 
server, subtending  an  angle  as  much  greater  than 
that  at  the  point  0,  as  is  the  magnifying  power 
of  the  telescope. 

In  place  of  the  eye-piece  of  four  lenses,  which 


28 


THE  VERNIER  TRANSIT. 


we  have  just  been  considering,  and  which  is  exclusively  used  in 
all  American  instruments  made  at  the  present  day ; another, 
which  has  but  three  lenses,  is  often  seen  in  the  telescopes  of 
imported  instruments. 

This  latter,  which  inverts  the  object,  though  saving  a little 
more  light  than  the  former,  is  exceedingly  troublesome  to  the 
inexperienced  observer,  and  has  never  been  popular  in  American 
Engineering. 

To  ascertain  the  Magnifying  Power  of  a Telescope, 

Set  up  the  instrument  about  twenty  or  thirt}^  feet  from  the  side 
of  a white  wooden  house,  and  observe  through  the  telescope  the 
space  covered  by  one  of  the  boards  in  the  field  of  the  glass  ; then, 
still  keeping  that  eye  on  the  telescope,  hold  open  the  other  with 
the  finger,  if  necessary,  and  look  with  it  at  the  same  object.  By 
steady  and  careful  observation  there  will  appear  on  the  surface 
of  the  magnified  board,  a number  of  smaller  ones  seen  by  the 
naked  eye,  count  these,  and  we  shall  obtain  the  magnifying 
power. 

If  the  limits  of  the  magnified  board,  as  seen  throuo-h  the  tele- 
scope,  can  be  noted  so  as  to  be  remembered  after  the  eye  is  removed, 
the  number  of  boards  contained  in  this  space  may  then  be  easily 
counted. 

The  side  of  an  unpainted ‘brick  wall,  or  any  other  surface,  con- 
taining a number  of  small,  well  marked  and  equal  objects,  may  be 
observed,  in  place  of  the  surface  we  have  described. 

Tlie  operation  described  requires  great  care  and  close  observa- 
tion, but  may  be  performed  with  facility  after  a little  practice. 

We  have  spoken  of  tlie  effect  of  tlie  telescope  in  magnifying 
objects,  but  have  not  mentioned  what  is  termed  its  “ illuminating 
power.” 

This  arises  from  the  great  diameter,  or  aperture  of  the  object- 
glass,  compared  witli  that  of  tlie  pupil  of  the  eye,  whicli  enables 
the  observer  to  intercept  many  more  rays  of  light,  and  bring  the 
object  to  the  eye  highly  illuminated. 


THE  VERNIER  TRANSIT. 


29 


The  advantage  gained  in  this  increase  of  light  depends,  as  is  evi- 
dent, on  the  size  of  the  object  glass,  and  the  perfection  with  which 
the  lenses  transmit  the  light  without  absorbing  or  reflecting  it. 

The  superficial  magnifying  power  of  a telescope,  is  found  by 
gquaring  the  number  which  expresses  its  linear  magnifying  power ; 
thus  a telescope  which  magnifies  twenty  times,  increases  the  sur- 
face of  an  object  four  hundred  times. 

Before  an  observation  is  made  with  the  telescope,  the  eye- 
piece should  be  moved  in  or  out,  until  the  wires  appear  distinct 
to  the  eye  of  the  operator ; the  object  glass  is  then  adjusted  by 
turning  the  pinion  head  until  the  object  is  seen  clear  and  well 
defined,  and  the  wires  appear  as  if  fastened  to  its  surface. 

The  intersection  of  the  wires,  being  the  means  by  which  the 
optical  axis  of  the  telescope  is  defined  should  be  brought  pre- 
cisely upon  the  centre  of  the  object  to  which  the  instrument  is 
directed. 

Having  thus  briefly  considered  the  principles,  we  shall  now  pro- 
ceed to  describe  the 

Attachments  of  the  Telescope, 

A telescope  is  said  to  be  plain”  when  it  is  without  any  ap- 
pendages to  its  tube  or  axis,  as  the  Engineers’  Transit  shown  on 
the  frontispiece,  and  mos-t  instruments  are  made  in  that  manner. 

Many  surveyors,  however,  prefer  to  add  these  conveniences, 
and  we  shall  now  consider  them  in  detail. 

Clamp  and  Tangent. — This  consists  essentially  of  a ring,  en- 
circling the  axis  of  the  telescope,  and  having  two  projecting 
arms,  the  one  above  being  slit  through  the  middle  and  holding 
the  clamp  screw,  the  other  much  longer  and  below,  is  connected 
with  the  tangent  screw. 

As  soon  as  the  clamp  screw  is  tightened,  the  ring  is  brought 
firmly  around  the  axis,  and  the  telescope  can  then  be  moved  up 
or  down  by  turning  the  tangent  screw. 

The  clamp  and  tangent  ought  always  to  accompany  the  vertical 
circle  and  the  level  on  the  telescope. 

3^ 


30 


THE  VERNIER  TRANSIT. 


V ERTiCAL  Circle. — A divided  circle  as  seen  in  the  cut  of  the 
Vernier  Transit,  is  often  attached  to  the  axis  of  the  telescope, 
giving,  with  a vernier,  the  means  of  measuring  vertical  angles 
with  great  facility. 

We  make  two  sizes  of  these  circles,  one  of  about  3^  inches 
diameter,  seen  with  this  instrument,  the  other  an  inch  larger,  and 
shown  in  the  cut  of  the  Engineer’s  Transit,  Fig.  12.  The  former 
is  graduated  to  single  degrees,  and  reads,  by  the  vernier,  to  five 
minutes  of  a degree.  The  latter,  divided  to  half  degrees,  gives  a 
reading,  with  the  vernier,  to  single  minutes. 

The  vertical  circle  is  fitted  firmly  to  the  telescope  axis,  and 
fastened  with  a screw,  so  that  it  remains  permanent. 

The  vernier  however,  may  be  shifted  in  either  direction,  by 
loosening  the  screws  which  confine  it  to  the  standards. 

The  vernier  of  the  small  circle  is  divided  into  twelve  equal 
parts,  which  correspond  with  thirteen  degrees  on  the  circle. 

Each  division  of  the  vernier  is,  therefore,  one-twelfth  of  one 
degree,  or  five  minutes  longer  than  a single  divison  of  the  circle, 
so  that  the  angles  are  read  to  five  minutes  of  a degree. 

The  vernier  is  double,  having  its  zero  point  in  the  middle,  and 
the  reading  up  to  thirty  minutes,  is  said  to  be  direct ; that  is,  if  the 
circle  is  moved  to  the  right,  the  minutes  are  read  off  on  the  right 
side  of  the  vernier,  and  vice  versa. 

The  minutes  beyond  thirty  are  obtained  on  the  opposite  side, 
and  in  the  lower  row  of  figures. 

By  following  these  directions,  and  noticing  the  first  divisions  on 
the  circle  and  vernier,  which  exactly  correspond,  the  surveyor  can 
obtain  a reading  to  five  minutes,  with  great  facility. 

Level  on  Telescope. — Besides  the  vertical  circle,  there  is 
sometimes  a small  level  attached  to  the  telescope  of  this,  and  other 
instruments,  which  we  shall  hereafter  describe. 

Such  an  attachment  is  shown  in  the  cut  of  the  Surveyor’s  Tran- 
sit, and  its  adjustment  and  advantages  will  be  explained  in  our 
account  of  that  instrument. 


THE  VERNIER  TRANSIT. 


31 


Sights  on  Telescope. — We  are  sometimes  desired  by  survey- 
ors, to  place  a pair  of  short  sights  on  the  upper  side  of  the  tele- 
scope tube. 

They  are  best  made  to  fold  close  to  the  tube,  when  not  in  use, 
like  those  of  the  pocket  compass,  described  hereafter. 

These  sights  are  thought  to  be  useful  in  taking  back  sights 
without  turning  the  telescope,  and  in  sighting  l^hrough  bushes  or 
in  the  forest. 

We  believe,  however,,  that  a telescope  is  incomparably  better, 
in  every  situation,  and  would  never  advise  their  construction 
or  use.  f 

Sights  for  Right  Angles. — Besides  the  sights  just  mentioned, 
we  have  often  attached  others  to  the  plate  of  the  instrument,  on 
either  side  of  the  compass  circle,  or  on  the  standards. 

These  being  adjusted  to  the  telescope,  give  a very  ready  means 
of  laying  off  right  angles,  or  running  out  offsets,  without  chang- 
ing the  position  of  the  instrument. 

To  Adjust  the  Vernier  Transit, 

The  Levels  of  this  instrument  have  a capstan  head  screw  at 
each  end,  and  are  adjusted  with  a steel  pin  in  the  same  manner  as 
those  of  the  Plain  Compass. 

The  Needle  is  adjusted  as  described  in  our  account  of  the 
Plain  Compass. 

Line  of  Collimation. — To  make  this  adjustment,  which  is,  in 
other  words,  to  bring  the  intersection  of  the  wires  into  the  optical 
axis  of  the  telescope,  so  that  the  instrument,  when  placed  in  the 
middle  of  a straight  line  will,  by  the  revolution  of  the  telescope, 
cut  its  extremities — proceed  as  follows : 

Set  the  instrument  firmly  on  the  ground  and  level  it  carefully  ; 
and  then  having  brought  the  wires  into  the  focus  of  the  eye-piece, 
adjust  the  object-glass  on  some  well  defined  point,  as  the  edge  of 
a chimney,  or  other  object,  at  a distance  of  from  two  to  five 
hundred  feet;  determine  if  the  vertical  wire  is  plumb,  by  clamping 
the  instrument  firmly  to  the  spindle  and  applying  the  wire  to  the 


82 


THE  VERNIER  TRANSIT. 


vertical  edge  of  a building,  or  observing  if  it  will  move  parallel 
to  a point  taken  a little  to  one  side  ; should  any  deviation  be 
manifested,  loosen  the  cross- wire  screws,  and  by  the  pressure  of 
the  hand  on  the  heads  outside  the  tube,  move  the  ring  around 
until  the  error  is  corrected. 

The  wires  being  thus  made  respectively  horizontal  and  vertical, 
fix  their  point  of  intersection  on  the  object  selected  ; clamp  the 
instrument  to  the  spindle,  and  having  revolved  the  telescope,  find 
or  place  some  good  object  in  the  opposite  direction,  and  at  about 
the  same  distance  from  the  instrument  as  the  first  object  assumed. 

Great  care  should  always  be  taken  in  turning  the  telescope, 
that  the  position  of  the  instrument  upon  the  spindle  is  not  in  the 
slightest  degree  disturbed. 

Now,  having  found  or  placed  an  object  which  the  vertical  wire 
bisects,  unclamp  the  instrument,  turn  it  half  way  around,  and 
direct  the  telescope  to  the  first  object  selected  ; having  bisected 
this  with  the  wires,  again  clamp  the  instrument,  revolve  the 
telescope,  and  note  if  the  vertical  wire  bisects  the  second  object 
observed. 

Should  this  happen,  it  will  indicate  that  the  wires  are  in  adjust- 
ment, and  the  points  bisected  are  with  the  centre  of  the  instru- 
ment, in  the  same  straight  line. 

If  not,  however,  the  space  which  separates  the  wdres  from  the 
second  point  observed,  will  be  double  the  deviation  of  that  point 
from  a true  straight  line,  which  may  be  conceived  as  drawn 
through  the  first  point  and  the  center  of  the  instrument,  since  the 
error  is  the  result  of  two  observations,  made  with  the  wires  when 
they  are  out  of  the  optical  axis  of  the  telescope. 

Fig.  8. 


F^or  as  in  the  diagram,  let  A represent  the  centre  of  tlie  instru- 


THE  VERNIER  TRANSIT. 


33 


nient,  and  B 0 tlie  imaginary  straight  line,  upon  the  extremities 
of  which  the  line  of  collimation  is  to  he  adjusted. 

B represents  the  object  first  selected,  and  D the  point  which  tlie 
wires  bisected,  when  the  telescope  was  made  to  revolve. 

When  the  instrument  is  turned  half  around,  and  the  telescope 
again  directed  to  B,  and  once  more  revolved,  the  wires  will  bisect 
an  object,  E,  situated  as  far  to  one  side  of  the  true  line  as  the  point 
D is  on  the  other  side. 

The  space,  D E,  is  therefore  the  sum  of  two  deviations  of  the 
wires  from  a true  straight  line,  and  the  error  is  made  very  appa- 
rent. 

In  order  to  correct  it,  use  the  two  capstan  head  screws  on  the 
sides  of  the  telescope,  these  being  the  ones  which  affect  the  posi- 
tion of  the  vertical  wire. 

Eemember  that  the  eye-piece  inverts  the  position  of  the  wires, 
and  therefore,  that  in  loosening  one  of  the  screws,  and  tightening 
the  other  on  the  opposite  side,  the  operator  must  proceed  as  if  to 
increase  the  error  observed.  Having  in  this  manner  moved  back 
the  vertical  wire  until,  by  estimation,  one-quarter  of  the  space, 
D E,  has  been  passed  over,  return  the  instrument  to  the  point,  B, 
revolve  the  telescope,  and  if  the  correction  has  been  carefully 
made,  the  wires  will  now  bisect  a point,  C,  situated  midway  be- 
tween D and  E,  and  in  the  prolongation  of  the  imaginary  line, 
passing  through  the  point  B and  the  centre  of  the  instrument. 

To  ascertain  if  such  is  the  case,  turn  the  instrument  half  around, 
fix  the  telescope  upon  B,  clamp  to  the  spindle,  and  again  revolve 
the  telescope  towards  C.  If  the  wires  again  bisect  it,  it  will 
prove  that  they  are  in  adjustment,  and  that  the  points  B,  A,  C, 
all  lay  in  the  same  straight  line. 

Should  the  vertical  wire  strike  to  one  side  of  C,  the  error  must 
be  corrected  precisely  as  above  described,  until  it  is  entirely  re- 
moved. 

Another  method  of  adjusting  the  line  of  collimation,  often 
employed  in  situations  where  no  good  points  in  opposite  directions 


34 


THE  VERNIER  TRANSIT. 


can  be  selected  upon  which  to  reverse  the  wires,  may  here  be 
described. 

The  operator  sets  up  the  instrument  in  • some  position  which 
commands  a long  sight  in  the  same  direction,  and  having  leveled 
his  instrument,  clamps  to  the  spindle,  and  with  the  telescope 
locates  three  points  which  we  will  term  A,  B,  and  C,  which  are 
distant  from  the  instrument  about  one,  two,  and  three  hundred 
feet,  respectively. 

These  points,  which  are  usually  determined  by  driving  a nail 
into  a wooden  stake  set  firmly  into  the  ground,  will  all  lie  in  the 
game  straight  line,  however  much  the  wires  are  out  of  adjustment, 
since  the  position  of  the  instrument  remains  unchanged  during 
the  whole  operation. 

Having  fixed  these  points,  he  now  moves  the  instrument  to  B, 
End  sets  its  centre  directly  over  the  nail  head,  by  letting  down 
upon  it  the  point  of  a plumb-bob  suspended  from  the  tripod. 

Then  having  leveled  the  instrument,  he  directs  the  wires  to  A, 
clamps  to  the  spindle,  and  revolves  the  telescope  towards  C. 
Should  the  wires  strike  the  nail  at  that  point,  it  would  show  that 
they  were  in  adjustment. 

Should  any  deviation  be  observed,  the  operator  must  correct 
it  by  moving  the  wire  with  the  screws  until,  by  estimation,  half 
the  error  is  removed. 

Then  bringing  the  telescope  again  upon  either  A or  C,  and 
revolving  it,  he  will  find  that  the  wires  will  strike  the  point  in 
the  opposite  direction,  if  the  proper  correction  has  been  applied. 

If  not,  repeat  the  operation  until  the  telescope  will  exactly  cut 
the  two  opposite  points,  when  the  intersection  of  the  wfires  will 
V)e  in  the  optical  axis,  and  the  line  of  collimation  in  adjustment. 

In  our  description  of  the.  previous  operation,  we  have  spoken 
more  particularly  of  tlic  vertical  wire,  because  in  a revolving 
telescope  this  occupies  the  most  important  place,  the  horizontal 
one  being  employed  mainly  to  define  the  centre  of  the  vertical 


THE  VERNIER  TRANSIT. 


35 


wire,  so  that  it  may  be  moved  either  up  or  down  without  materi- 
ally disturbing  the  line  of  collimation. 

The  wires  being  adjusted,  their  intersection  may  now  be  brought 
into  the  centre  of  the  field  of  view. 

The  Eye-piece,  is  centred  by  moving  the  screws  A A,  shown 
in  the  sectional  view  of  the  telescope.  Fig.  4,  which  are  slackened 
and  tightened  in  pairs,  the  movement  being  now  direct,  until  the 
wires  are  seen  in  their  proper  position. 

It  is  here  proper  to  observe  that  the  position  of  the  line  of  col- 
limation depends  upon  that  of  the  object-glass,  solely,  so  that  the 
eye-piece  may,  as  in  the  case  just  described,  be  moved  in  any 
direction,- or  even  entirely  removed  and  a new  one  substituted, 
without  at  all  deranging  the  adjustment  of  the  wires. 

The?  Standards. — In  order  that  the  wires  may  trace  a vertical 
hne  as  the  telescope  is  moved  up  or  down,  it  is  necessary  that  both 
the  standards  of  the  telescope  should  be  of  precisely  the  same 
height.  ' 

To  ascertain  this  and  make  the  correction  if  needed,  proceed  as 
follows  : 

Having  the  line  of  collimation"  previously  adjusted,  set  the 
instrument  in  a position  where  points  of  observation,  such  as  the 
point  and  base  of  a lofty  spire,  can  be  selected,  giving  a long 
range  in  a vertical  direction. 

Level  the  instrument,  fix  the  wires  on  the  top  of  the  object, 
and  clamp  to  the  spindle ; then  bring  the  telescope  down,  until 
the  wires  bisect  some  good  point,  either  found  or  marked  at  the 
base  ; turn  the  instrument  half  around,  fix  the  wires  on  the  lower 
point,  clamp  to  the  spindle,  and  raise  the  telescope  to  the  highest 
object. 

If  the  wires  bisect  it,  the  vertical  adjustment  is  effected ; if 
they  are  thrown  to  either  side,  this  would  prove  that  the  standard 
opposite  that  side,  was  the  highest,  the  apparent  error  being 
double  that  actually  due  to  this  cause. 


86 


THE  VERNIER  TRANSIT. 


To  correct  it,  we  now  make  one  of  the  bearings  of  the  axis 
movable,  so  that  by  turning  a screw  underneath  this  sliding  piece 
as  well  as  the  screws  which  hold  on  the  cap  of  the  standard,  the 
adjustment  is  made  with  the  utmost  precision. 

This  arrangement  which  is  common  to  all  our  telescope  instru- 
ments is  very  substantial  and  easily  managed. 

The  Vertical  Circle. — 'When  this  attachment  requires  ad- 
justment, proceed  by  leveling  the  instrument  carefully,  and  having 
brought  into  line  the  zeros  of  the  wheel  and  vernier,  find,  or  place 
gome  well  defined  point,  or  line,  wdiich  is  cut  by  the  horizontal 
wire. 

Turn  the  instrument  half  around,  revolve  the  telescope,  and 
fixing  the  wire  upon  the  same  point  as  before,  note  if  the  zeros 
are  again  in  line. 

If  not,  loosen  the  screws,  and  move  the  zero  of  the  vernier 
over  half  the  error  ; bring  the  zeros  again  into  coincidence,  and 
proceed  precisely  as  at  first  described,  until  the  error  is  entirely 
corrected,  when  the  adjustment  will  be  completed. 

Should  it  be  desired,  at  any  time,  the  circle  can  be  removed 
Fy  the  surveyor,  and  replaced  at  pleasure. 

The  Level  on  Telescope. — The  adjustment  of  this  will 
be  best  considered  wdien  we  come  to  speak  of  the  Surveyors 
Transit. 

Adjustments  in  General. — "We  ought  here  to  say,  that  the 
above  adjustments,  as  well  as  all  the  others  which  we  have  pre- 
viously explained  or  may  hereafter  describe,  are  always  made  by 
us  in  person,  but  are  given  in  this  work  in  order  that  the  Sur- 
veyor and  Engineer  may  fully  understand  their  instruments,  and 
be  enabled  to  detect  and  remedy  errors  and  accidents  wliich  in 
practice  will  often  occur. 

To  Use  the  Vernier  Transit. 

ddiis  instrument  is  used  on  the  ordinary  ball  and  spindle  placed 
most  commonly  in  the  compass  trit)od  as  shown  in  Fig.  3. 


THE  VERNIER  TRANSIT. 


87 


Tripod  Head. — Sometimes  leveling  screws  with  the  parallel 
plates,  and  which  together  we  shall  designate  the  “tripod  head’* 
with  a clamp  and  tangent  movement,  are  used  with  tliis  instru- 
ment as  w^ell  as  with  the  Surveyors  Transit. 

This  tripod  head  can  be  unscrewed  from  the  legs,  and  is  packed 
in  the  instrument  box  ; it  is  of  very  moderate  cost,  and  in  almost 
every  situation  is  infinitely  superior  to  a ball  and  socket  support. 

Ball  and  Socket. — This  we  also  make  in  all  cases  where  the 
tripod  head  is  furnished,  by  cutting  a screw  upon  the  lower  end 
of  the  Jacob  staff,  a ball  and  spindle  being  also  supplied  so  that  the 
Surveyor  can  use  the  same  instrument  either  upon  a Jacob  staff, 
a compass  tripod,  or  a leveling  tripod. 

Compound  Ball. — AYe  also  manufacture 
what  may  be  termed  a “ compound  ball  spin- 
dle,” which  has  a tangent  movement,  and 
gives  all  the  perfection  of  more  costly  arrang- 
ments,  with  a very  moderate  expense. 

As  represented  in  the  cut,  it  has  an  interior 
spindle,  around  which  an  outside  hollow  cyl- 
inder is  moved,  by  turning  tlie  double-headed 
tangent  screw,  which  has  in  the  middle,  an 
endless  screw,  working  into  teelh,  cut  spirally 
around  in  a groove  of  the  cylinder.  The 
compass,  or  other  instrument,  revolves  on  the 
outside  socket,  precisely  as  if  placed  on  a 
[Fig.  9.]  common  ball  spindle ; but  when  a slower 
movement  is  recpiired,  can  be  made  fast  by  the  clamp  screw,  and 
then  turned  gradually  around  the  interior  spindle,  by  the  tangent 
screw,  until  the  slote  of  tlie  sight,  or  the  intersection  of  the  wires, 
is  made  to  bisect  the  object  with  the  utmost  certainty. 

The  compound  ball  may  be  placed  either  in  a Jacob-staff  socket, 
or  compass  tripod. 

The  Spring  Catch,  described  in  our  account  of  the  Plaiu 
Compass,  is  always  attached  to  the  socket  of  this  instrument^ 

4 


38 


THE  VERNIER  TRANSIT. 


whether  placed  upon  a ball  or  tripod,  so  that  it  cannot  slip  off 
from  the  spindle  in  carrying. 

The  Clamp  Screw,  in  the  side  of  the  socket  of  this  instru- 
ment, is  shown  in  Fig.  3,  and  by  pressing  a brass  spring  in  the 
interior  against  the  spindle,  serves  to  fix  the  instrument  in  any 
position. 

The  Vernier  is  moved  b}^  the  tangent  screw,  now  always, 
placed  above  the  plate,  precisely  as  described  in  our  account  of 
the  Vernier  Compass,  and  is  read  to  minutes  in  the  same  manner. 

There  is  also  a clamp  nut  underneath  the  vernier,  by  which 
it  is  securely  fixed  in  any  position,  which  must  be  loosened  when- 
ever the  vernier  is  moved  by  the  tangent  screw. 

The  Needle  Lifting  Screw  is  the  same  as  those  of  the 
compasses  previously  described. 

In  Surveying  with  this  instrument,  the  operator  proceeds 
precisely  as  with  the  Vernier  Compass,  keeping  the  south  end 
towards  his  person,  reading  the  bearings  of  lines  from  the  north 
end  of  the  needle,  and  using  the  telescope  in  place  of  sights,  re- 
volving it  as  objects  are  selected  in  opposite  directions. 

Parallax. — Before  an  observation  is  made  with  the  telescope, 
the  eye-piece  sliould  be  moved  in  or  out  until  the  wires  appear 
distinct  to  the  eye  of  the  operator ; the  object-glass  may  then  be 
placed  in  position,  by  turning  the  pinion  head  on  the  top  of  the 
telescope  until  the  object  is  seen  clear  and  well  defined,  and  the 
wires  appear  as  if  fastened  to  its  surface. 

When  on  the  contrary,  the  wires  are  not  perfectly  distinct,  the 
observer  by  moving  his  eye  to  either  side  of  the  small  aperature 
of  the  eye-piece  will  cause  the  wires  to  “ travel  ” on  the  object, 
and  thus  occasion  what  is  termed  the  error  of  parallax.” 

Tlie  intersection  of  the  wires  being  the  means  by  which  the 
optical  axis  of  the  telesco})c  is  defined,  should  be  brought  pre- 
cisely uopn  the  centre  of  the  object  to  which  the  instrument  is 
directed. 


THE  VERNIER  TRANSIT. 


80 


To  TAKE  Angles  of  Elevation. — Level  the  instrument  care- 
fullv,  fix  the  zeros  of  the  circle  and  vernier  in  line,  and  note  the 
height  cut  upon  the  staff  or  other  object  bj  the  horizontal  wire  ; 
then  cany  the  staff  up  the  elevation,  fix  the  wire  again  upon  the 
same  point,  and  the  angle  of  elevation  will  be  read  off  bv  the 
vernier. 

By  careful  usage,  the  adjustments  of  the  vernier  transit  will 
remain  as  permanent  as  those  of  the  ordinary  compass,  the  only 
one  liable  to  derangement,  being  that  of  the  line  of  collimation. 

This  should  be  examined  occasionally,  and  corrected  in  the 
manner  previously  described. 

Repairs  of  the  Vernier  Transit 

These  being  in  great  part  already  spoken  of,  it  will  be  neces- 
sary to  consider  only  such  as  belong  to  the  telescope. 

To  Replace  the  Cross-Wires. — Take  out  the  eye-piece  tube, 
together  with  the  little  ring  by  wliich  it  is  centred,  and  having 
removed  two  opposite  cross-wire  screws,  with  the  otliers  tiirn  tlie 
ring  until  from  the  open  end  of  the  telescope  tube,  one  of  the 
screw  holes  is  brouglit  into  view ; in  this  thrust  a stout  splinter 
of  wood  or  a small  wire,  so  as  to  hold  the  ring  while  the  other  ' 
screws  are  withdrawn  ; the  ring  is  then  taken  out  and  is  ready  for 
the  wires. 

For  these  the  web  of  the  spider  is  to  be  preferred  above  any 
thing  else,  but  when  this  is  not  obtainable,  a fine  silk  fibre  may 
be  substituted. 

We  usually  procure  our  webs  from  the  living  manufacturer 
directly,  selecting  those  of  a yellowish-brown  color  as  furnishing 
the  most  perfect  product. 

The  spider  being  held  between  the  thumb  and  finger  of  an 
assistant,  in  such  position  as  to  suffer  no  serious  injury,  and  at  the 
same  time  be  unable  to  make  any  effectual  resistance  Avitli  his 
extremities,  the  little  fibre  may  be  drawn  out  at  pleasure,  and 
being  placed  in  the  fine  lines  cut  on  the  surfuce  oT  the  diaphragm, 
is  then  firmly  cemented  to  its  place  by  applying  softened  beeswax 
with  the  point  of  a knife  blade. 


40 


THE  VERNIER  TRANSIT. 


In  case  the  spider  is  not  procurable,  a fine  strand  of  a web 
which  is  free  from  dust,  and  long  enough  to  serve  for  both  wires, 
may  be  selected. 

In  such  times  as  the  spiders  remain  in  their  winter  quarters,  we 
have  been  able  to  procure  very  good  fibres  from  a box  in  which 
a number  had  been  confined. 

When  the  wires  are  cemented,  the  ring  is  returned  to  its  posi- 
tion in  the  tube,  and  either  pair  of  screws  being  inserted,  the 
splinter  or  wire  is  removed  and  the  ring  turned  until  the  other 
screws  can  be  replaced. 

Care  must  also  be  taken  that  the  same  side  of  the  ring  is  turned 
to  the  eye-piece  as  before  it  was  removed. 

When  tliis  has  been  done,  the  eye-tube  is  inserted  and  its  cen- 
tering ring  brought  into  such  a position  that  the  screws  in  it  can 
be  replaced,  and  then  by  screwing  on  the  end  of  the  telescope, 
the  little  cover  into  which  the  eye  tube  is  screw^ed,  the  operation 
will  be  completed. 

To  Clean  the  Telescope. — The  only  glasses  that  w^ill  ordi- 
narily require  cleaning  are  the  object-glass  on  its  outside  surface, 
» and  the  little  eye  lens,  which  is  exposed  when  the  cap  of  the  eye 
tube  is  removed. 

To  remove  the  dust  from  these  use  a very  soft  and  clean  silk  or 
cotton  cloth,  and  be  careful  not  to  rub  the  same  part  of  the  cloth 
a second  time  on  the  surface  of  the  glass. 

No  one  should  ever  be  allowed  to  touch  the  glasses  with  the 
fingers  or  with  a dusty  cloth. 

Excellencies  of  the  Vernier  Transit. 

These  are  due  chiefly  to  the  telescope  and  its  attachments,  and 
from  what  has  been  already  said,  it  will  appear  are  such  as  to 
render  this  instrument  greatly  superior  to  one  provided  with  the 
ordinary  sights. 

1.  The  magnifying  power  of  the  telescope  enables  the  surveyor 
to  take  accurate  observations  at  distances  entirely  beyond  the 
reacli  of  the  naked  eye. 


THE  VERNIER  TRANSIT. 


41 


2.  The  fine  intersection  of  the  cro^s-wires  can  be  set  precisely 
upon  the  centre  of  the  object. 

3.  The  revolving  property  of  the  telescope  gives  the  means  of 
running  long  lines  up  or  down  steep  ascents  or  descents  with  per- 
fect ease,  where,  with  the  short  sights  of  the  ordinary  compass, 
two  or  three  observations  would  have  to  be  taken. 

4.  The  use  of  a telescope  entirely  avoids  the  incessant  trying 
of  the  eyes,  experienced  in  surveys  with  the  ordinary  sights. 

5.  With  the  telescope,  lines  can  be  run  through  the  forest  or 
brushwood,  and  the  flagstaff  distinguished  with  much  greater  cer- 
tainty than  through  the  sights  of  a compass. 

This  statement  may  appear  very  unreasonable  to  those  not 
familiar  with  the  instrument,  and  these  in  fact,  raise  the  greatest 
objection  to  a telescope,  from  its  supposed  unfitness  for  surveys  in 
such  locations. 

They  have  only  to  use  it  a few  times  in  this  kind  of  work,  in 
connection  with  a flagstaff  painted  white  or  covered  with  paper, 
to  distinguish  it  from  the  surrounding  objects,  to  be  convinced  of 
its  great  superiority. 

In  the  Vernier  Transit,  as  furnished  by  us,  is  supplied,  as  we 
believ^e  to  the  surveyor,  the  most  perfect  of  all  needle  instruments, 
and  this  at  a cost  but  little  above  that  chait’ged  by  other  makers 
for  a sight  compass. 

The  advantages  of  the  telescope  and  its  attachments  are  so 
great,  that  a surveyor,  accustomed  to  tliem,  would  find  it  difficult 
to  content  liimself  witli  the  ordinary  compass,  and  such  in  fact  is 
the  universal  testimony  of  tliose  familiar  witli  the  Vernier  Transit. 

Weight  of  the  Vernier  Transit. 

The  weight  of  this  instrument,  exclusive  of  the  tripod  legs, 
and  plain  telescope,  is  about  10  lbs. 


4* 


NEEDLE  INSTRUMENTS. 


We  have  now  described  the  instruments  included  under  the 
division  termed  Needle  Instruments,  in  the  beginning  of  this 
work. 

As  there  stated,  the  Plain  and  Vernier  Compasses  and  the 
Vernier  Transit  depend  for  their  accuracy  and  value,  mainly  upon 
the  perfection  of  movement  of  the  magnetic  needle. 

With  such  instruments,  the  greater  part  of  the  surveying  in  our 
country  has  been,  and  will  for  a long  time  in  the  future,  continue 
to  be  done. 

And  though  with  the  improvements  made  in  these  instruments, 
a good  surveyor  may,  with  great  care  and  skill,  do  work  with  a 
surprising  degree  of  accuracy  and  perfection,  yet  all  needles  are 
liable  to  many  irregularities. 

Imperfections  of  the  Needle, 

These  may  arise  either  from  the  loss  of  magnetic  virtue  in  the 
poles,  the  blunting  of  tlie  centre-pin,  or  the  attraction  exerted 
upon  it  by  bodies  of  iron  whose  presence  may  be  entirely  unsus- 
pected. 

Tlie  two  first  of  these  errors  may  be  easily  remedied  in  the 
manner  we  have  described. 

Local  Attraction. — The  third  and  most  frequent  source  of 
inaccuracy,  may  be  detected  by  taking  back  sights  as  well'as  fore 
sights  u[)on  ev(.‘ry  line  run  with  the  needle,  and  by  the  agreement 
of  the  bearings  the  true  direction  of  the  line  will  be  determined. 

Sometimes  a compass  may  have  little  particles  of  iron  concealed 
within  the  surface  of  the  metal  circle  or  plates. 

It  is  the  business  of  the  maker  to  examine  every  instrument. 


NEEDLE  INSTRUMENTS. 


43 


in  search  of  this  defect,  by  trying  the  reversion  of  the  needle 
upon  all  points  of  the  divided  circle. 

If'^he  needle  should  fail  to  reverse  when  the  compass  is  turned 
half  around  and  the  sights  directed  a second  time  upon  any  object, 
the  instrument  should  be  thrown  aside  and  never  sold. 

Besides  the  difficulties  caused  by  the  above  imperfections,  the 
variation  of  the  needle  is  a frequent  source  of  annoyance. 

What  is  termed  the  secular  variation,  we  have  already  men- 
tioned in  our  account  of  the  Yernier  Compass,  we  will  now  speak 
of  the 

Diurnal  Yariation. — This  is  owing  to  the  influence  of  the 
sun,  which  in  summer  will  cause  the  needle  to  vary  from  ten  to 
fifteen  minutes  in  a few  hours,  when  exposed  to  its  fullest  influ' 
ence. 

To  guard  against  these  causes  of  inaccuracy  in  the  use  of 
needle  instruments,  the  surveyor  will  need  the  greatest  care  and 
attention ; and  yet,  with  all  the  precautions  that  can  be  suggested, 
the  difficulty  of  measuring  horizontal  angles  with  certainty,  and 
to  a sufficient  degree  of  minuteness  by  the  needle  alone,  has  caused 
a demand  to  be  felt  more  and  more  sensibly  in  all  parts  of  the 
country  for  instruments,  in  the  use  of  which,  the  surveyor  may 
proceed  with  assured  accuracy  and  precision. 

Indeed,  in  Canada,  so  great  is  the  distrust  of  needle  instru- 
ments, that  the  Provincial  Land  Surveyors  are  forbidden  to  use 
an  instrument  in  their  land  surveys,  unless  it  is  capable  of  taking 
angles  independently  of  the  needle. 

To  supply  the  demand  thus  created  for  increased  perfection  in 
the  implements  of  the  surveyor,  w^e  manufacture  a variety  of 
instruments:  two  of  which  we  shall  now  describe,  under  tlie 
names  of  The  Railroad  Compass^  and  The  Surveyors*  Transit, 


SURVEYING  INSTRUMENTS. 


THE  RAIL  ROAD  COMPASS. 


Fig.  10. 


As  shown  in  Fig.  10,  this  iiistnnnent  lias  tlie  main  plate,  levels, 
sights,  and  needle  of  the  ordinary  instrument,  but  is  also  provided 
with  a circ'le  on  the  outside  of  the  compass  box,  divided  all  around 
and  reading  by  two  opposite  verniers  to  single  minutes  of  a 
degree. 

The  openings  through  which  the  divided  circle  and  verniers  are 
seen,  arc  closed  by  jilates  of  glass,  so  as  to  effectually  exclude  the 
dust  and  moisture;  the  openings  are  now  made  on  the  sides,  at 
right  angles  to  the  jiosition  they  occupy  in  the  cut,  in  order  to 
read  tlic  divisions  with  greater  convenience. 


THE  RAIL  ROAD  COMPASS. 


45 


The  verniers  are  fixed  to  the  main  plate,  and  this,  bj  a contrb 
vance  of  our  own  invention,  lias  long  sockets  which  give  it  great 
stability,  and  a motion  around  the  circle  almost  perfectly  free  from 
friction. 

In  this  arrano;ement,  the  compass  circle  is  very  firmly  attached 
to  the  socket,  of  which  the  lower  part  only  is  seen  in  the  cut. 

The  vernier  or  main  plate  moves  around  the  divided  circle  or 
limb,  the  divisions  on  both  vernier  and  limb  being  horizontal  and 
in  the  same  plane. 

There  is  also,  beneath  the  main  plate,  a clamp  and  tangent 
movement,  by  which,  after  the  main  plate  has  been  moved  nearly 
in  position  by  the  hand,  it  can  be  clamped  to  the  socket,  then 
with  the  tangent  screw,  the  verniers  are  moved  slowly  around 
the  limb,  and  the  sights  fixed  upon  the  desired  object  with  the 
greatest  precision. 

The  graduated  circle  or  limb  is  divided  to  half  degrees,  and 
figured  in  two  rows,  viz:  from  0^  to  90^,  and  from  0®  to  360^; 
sometimes  but  a single  series  is  used,  and  then  the  figures  run 
from  0^  to  360°,  or  from  0®  to  180°  on  each  side. 

The  figuring,  which  is  the  same  upon  this  as  in  the  other  angu- 
lar instruments  we  shall  hereafter  describe,  is  varied  according  to 
the  taste  of  the  engineer,  the  first  method  is  our  usual  practice. 

Tue  Verniers  are  double,  having  on  each  side  of  the  zero 
mark  thirty  equal  divisions,  corresponding  precisely  with  twenty- 
nine  half  degrees  on  the  limb. 

They  thus  read  to  single  minutes,  and  the  number  passed  over 
is  counted  from  the  zero  mark  in  the  same  direction  in  which  the 
vernier  is  moved. 

The  use  of  two  opposite  verniers  in  this  and  other  instruments 
gives  the  means  of  “cross  questioning”  the  graduations,  the  per- 
fection with  which  they  are  centred,  and  the  dependence  which 
can  be  placed  on  the  accuracy  of  tlie  angles  indicated. 

The  movement  of  the  vernier  plate  with  the  sights  attached 
around  the  compass  circle,  gives  the  surveyor  the  power  of  laying 


46 


THE  KAIL  KOAD  COMPASS. 


off  the  variation  of  the  needle,  while  the  graduated  circle  enables 
him  to  take  horizontal  angles  with  great  accuracy  and  minute- 
ness, entirely  independent  of  the  needle. 

The  Needle  of  this  instrument  is  about  five  and  a half  inches 
long,  and  made  precisely  like  those  previously  described. 

The  Adjustments  of  this  instrument,  with  which  the  surveyor 
will  have  to  do,  have  been  already  described. 

To  TJse  the  Rail  RooA  Compass. 

It  can  be  set  upon  the  common  compass  ball,  or  still  better,  the 
tangent  ball  already  described,  placed  either  in  a jacob-staff 
socket,  or,  as  most  surveyors  prefer,  in  a compass  tripod. 

W'  e have  also  adapted  to  many  of  these  instruments,  the  level- 
ing tripod  head,  with  clamp  and  tangent  movement  described  on 
page  50,  and  this  is  preferable  to  any  other  support. 

To  Take  Horizontal  Angles. — First  level  the  plate  and  set 
the  limb  at  zero,  fix  the  sights  upon  one  of  the  objects  selected, 
and  clamping  the  whole  instrument  firmly  to  the  spindle,  un- 
clamp the  vernier  plate  and  turn  it  with  the  hand,  until  the  sights 
are  brought  nearly  upon  the  second  object;  then  clamp* to  the 
limb,  and  with  the  tangent  screw  fix  them  precisely  upon  it. 

The  number  of  degrees  and  minutes  read  off  by  the  vernier, 
will  give  the  angle  betwmen  the  two  objects  taken  from  the  centre 
of  the  instrument. 

It  will  be  understood  that  the  horizontal  angles  can  be  taken 
in  any  position  of  the  verniers,  with  reference  to  the  zero  point 
of  the  limb  ; we  have  given  that  above  as  being  the  usual  method 
and  liable  to  the  fewest  errors. 

It  is  advisable  where  great  accuracy  is  re([uired,  in  this  and 
other  instruments  furnished  with  two  verniers,  to  obtain  the 
readings  of  the  limb  from  both,  add  the  two  together  and  halve 
their  sum  ; the  result  will  be  the  mean  of  the  two  readings,  and 
the  true  angle  between  the  points  observed. 


THE  RAIL  ROAD  COMPASS. 


47 


Such  a course  is  especially  necessary  when  the  readings  of  the 
verniers  essentially  disagree,  as  may  sometimes  happen  when  the 
instrument  has  been  injured  by  an  accident. 

To  Turn  off  the  Variation  of  the  Needle. — Having  lev- 
eled the  instrument,  set  the  limb  at  zero,  and  place  the  sights 
upon  the  old  line,  note  the  reading  of  the  needle,  and  make  it 
agree  with  that  given  in  the  field  notes  of  the  former  survey,  by 
turning  the  whole  instrument  upon  its  spindle. 

Now  clamp  to  the  spindle,  unclamp  the  vernier  plate  and  again 
fix  the  sights  upon  the  old  line;  the  number  of  degrees  or  min- 
utes passed  over  by  the  vernier,  will  be  tlie  change  ol  variation 
in  the  interval  betv/eeii  the  two  surveys. 

To  Survey  with  this  instrument,  the  operator  should  fix  the 
south  side  of  the  compass  face  towards  that  end  of  tlie  main  plate 
Avliich  has  the  spirit  level  placed  cross  wise,  and  having  brought 
the  zeros  of  the  limb  and  vernier  plate,  in  contact,  clamp  them, 
and  proceed  as  directed  in  our  account  of  the  Plain  Compass. 

Of  course,  it  will  be  understood  that  lines  can  be  run  and  angles 
measured,  by  the  divided  limb  and  verniers,  entirely  independent 
of  the  needle,  which,  in  localities  where  local  attraction  is  mani- 
fested, is  very  serviceable. 

The  accuracy  and  minuteness  of  the  horizontal  angles,  indicated 
by  tins  instrument,  together  with  its  perfect  adaption  to  all  the 
purposes  to  which  the  Vernier  Compass  can  be  applied,  have 
brou£:ht  it  into  use  in  rnanv  localities,  where  the  land  is  so  valuable 
as  to  require  more  careful  surveys  than  are  practicable  with  a 
needle  instrument. 

Weight  of  the  Rail  Road  Com2Jass, 

The  average  weight  of  this  instrument,  including  the  brass 
head  of  the  Jacob  staff,  is  about  11^  lbs. 


SURYEVISG  INSTRUMENTS. 


THE  SURVEYORS’  TRANSIT. 
Fig,  11. 


The  Surveyors’  Transit,  of  wiiicli  (he  above  cut  is  a represen- 
tation, is  in  ])rinciph*,  very  similar  to  tlie  instrument  just  described, 
difiering  from  it  mainly  in  the  sulistitution  of  the  telescope  with 
its  appendages,  for  the  ordinary  compass  sights. 


THE  SURVEYOES’  TRANSIT. 


49 


The  Telescope  is  of  somewhat  finer  quality  than  that  used 
with  the  Vernier  Transit;  as  here  shown,  it  is  furnished  with  a 
small  level,  having  a ground  bubble  tube  and  a scale ; sometimes, 
also  a vertical  circle  is  connected  with  its  axis. 

The  Standards  are  made  precisely  like  those  of  the  Y ernier 
Transit,  the  bearings  of  the  axis  of  the  telescope  being  conical, 
and  fitted  with  the  utmost  nicety ; there  is  also  in  one  of  them 
the  moveable  piece  for  the  adjustment  of  the  wires  to  the  tracing 
of  a vertical  line. 

The  Spirit  Levels  are  placed  above  the  upper  surface  of  the 
vernier  plate,  one  being  fixed  on  the  standard  so  as  not  to  obstruct 
the  light  which  falls  on  the  vernier  opening  beneath. 

Both  levels  are  adjustable  with  the  ordinary  steel  pin. 

The  Needle,  like  tliat  of  the  previous  instrument,  is  five  and 
a half  inches  long. 

The  Vernier  Plate,  which  carries  the  verniers  and  telescope, 
is  made  to  move  with  perfect  ease  and  stability  around  the  grad- 
uated circle  or  limb,  attached  to  the  compass  box,  thus  allowing 
the  telescope  and  verniers  to  be  set  to  any  variation  of  the  needle, 
and  turn  off  horizontal  angles  in  any  direction. 

The  Verniers,  as  in  all  our  angular  instruments,  are  double, 
readi]]g  either  way  from  the  centre  mark,  and  to  single  minutes  of 
a degree. 

There  are  two  verniers  placed  on  opposite  sides  of  the  instru- 
ment at  right  angles  to  the  telescope  ; only  one  of  these  is  shown 
in  the  cut. 

The  Divided  Circle,  or  limb,  is  graduated  to  half  degrees, 
reads  to  minutes  by  the  verniers,  and  is  figured  as  described  in 
our  account  of  the  previous  instrument. 

The  Clamp  and  Tangent  movement  of  the  vernier  plate  is 
the  same  as  that  of  the  Rail  Road  Compass ; it  is  partly  shown 
in  the  figure. 

The  Tripod  Head. — This  instrument  should  always  be  used 
on  a leveling  tripod. 

5 


50 


THE  SUKYEYORS’  TRANSIT. 


The  one  sliown  in  the  cut,  and  whicli  is  termed  the  Light  Level- 
ing Trii^od^  lias  the  upper  parallel  plate  thickened  on  its  under 
side,  so  as  to  give  a long  bearing  for  the  four  leveling  screws. 

The  under  plate  supports  the  feet  of  the  screws,  and  has  beneath 
a cavity  or  bowl,  in  wdiich  moves  a hemispherical  nut  screwed  to 
the  spindle  of  the  tripod. 

This  nut  serves  both  to  connect  the  plates  together,  and  as  a sup- 
port on  wdiich  the  upper  plate  is  moved  by  the  leveling  screws. 

The  under  parallel  plate  has  also  a screw  on  the  under  side,  by 
wdiich  the  tripod  head  may  be  disconnected  from  the  legs,  and 
packed  in  a box  wdth  the  instrument. 

The  leveling  screw^s  are  made  of  bell  metal,  have  a large  double 
milled  head  and  a deep  screw  of  about  forty  threads  to  the  inch  ; 
their  ends  set  into  little  brass  cups,  so  that  the  screws  are  worked 
without  indenting  the  under  plate.  Sometimes  a piece  of  leather 
is  put  in  place  of  the  cups. 

When  the  screw^s  are  loosened,  the  upper  plate  can  be  shifted 
around,  so  as  to  bring  the  leveling  screw^s  in  any  position  wdth 
reference  to  the  plates  and  telescope  of  the  instrument. 

The  clamp  and  tangent  screws  are  seen  on  the  upper  plate  of 
the  tripod.  In  place  of  the  single  tangent  screw,  we  have,  in  all  our 
later  instruments,  substituted  the  double  tangent  movement,  showm 
in  the  engraving  of  the  Engineers’  Transit  on  the  frontispiece. 

The  spindle  of  this  tripod  head  rises  above  the  upper  plate, 
and  the  instrument  can  be  removed  from  it  by  pulling  out  a little 
pin  made  to  spring  into  a groove,  and  thus  keep  the  instrument 
from  falling  when  the  tripod  is  carried  upon  the  shoulder. 

In  the  lower  end  of  the  spindle,  and  underneath  tlie  plates,  is 
screwed  tlie  loop  for  attaching  the  string  of  the  plumb-bob. 

In  the  operation  of  leveling  the  tripod,  the  engineer  takes  hold 
of  the  opposite  screw  heads  with  the  thumb  and  fore  finger  of  each 
hand,  and  turning  both  thumbs  in  or  out,  as  may  be  necessary, 
raises  one  side  of  tlie  ujiper  parallel  plate  and  depresses  the  other 
until  the  desired  correction  is  made. 


THE  surveyors’  TRANSIT. 


51 


To  Adjust  the  Surveyors'  Transit. 

The  Levels  are  adjusted  with  a steel  pin  as  those  of  the  Y er- 
nier  Transit,  and  it  need  only  be  added  here,  that  in  this  as  well 
as  other  instruments  having  two  plates  moving  upon  sockets  inde- 
pendent of  each  other,  the  levels,  when  adjusted  on  one  plate, 
should  still  keep  their  position  when  both  are  clamped  together 
and  turned  upon  a common  socket. 

Otherwise,  however  accurately  the  telescope  might  trace  a ver- 
tical line,  when  revolved  upon  the  socket  of  one  plate,  it  would 
give  a veiy  different  result  as  soon  as  the  position  of  the  other 
plate  was  changed. 

The  Needle  and  telescope  with  its  other  attachments  being 
adjusted,  as  described  in  our  account  of  the  Vernier  Transit,  we 
shall  here  consider  only  that  of  the 

Level  on  Telescope. — For  the  adjustment  of  this  attachment 
we  shall  give  two  methods,  the  first  being  that  usually  practiced 
by  us  : 

1.  First  level  the  instrument  carefully,  and  with  the  clamp  and 
tangent  movement  to  the  axis,  make  the  telescope  horizontal  as 
near  as  may  be  with  the  eye,  then  having  the  line  of  collimation 
previously  adjusted,  find  or  place  sonie  good  object  at  a conve- 
nient distance,  say  from  one  to  three  hundred  feet,  which  the  hori- 
zontal wire  will  bisect;  then,  without  moving  the  telescope,  turn 
the  instrument  upon  the  spindle,  and  with  the  same  wire  find  or 
place  another  object  in  the  opposite  direction,  and  at  the  same 
distance  from  the  instrument  as  the  first  point  selected. 

These  two  points  will  be  in  the  same  horizontal  line,  however 
much  the  telescope  may  be  out  of  level. 

Having  determined  these,  and  still  retaining  them,  remove  the 
instrument  one  or  two  hundred  feet  to  one  side  of  either  of  these 
points,  and  in  line  with  tliom,  level  it  again  and  bring  the  wires 
upon  the  nearest  object.  Then  turn  the  instrument  in  the  direction 
of  the  other,  and  note  the  position  of  the  horizontal  wire. 

If  it  does  not  bisect  the  point,  the  telescope  is  not  horiz^ontai, 


52 


THE  surveyors’  TRANSIT. 


and  the  wire  must  be  carried  back  over  half  the  error,  by  moving 
the  telescope  with  the  tangent  screw.  When  this  has  been  done, 
the  engineer  needs  only  to  alter  the  position  of  the  level,  by  the 
little  nuts  at  the  ends,  until  the  bubble  is  brought  into  the  centre 
of  the  tube,  when,  if  the  telescope  has  not  been  moved  from  the 
point  where  it  was  fixed,  the  adjustment  will  be  completed. 

2.  Choose  a piece  of  ground  nearly  level,  and  having  set  the 
instrument  firmly,  level  the  plates  carefully,  and  bring  the  bubble 
of  the  telescope  into  the  centre  with  the  tangent  screw.  Measure 
in  any  direction  from  the  instrument,  from  one  to  three  hundred 
feet,  and  drive  a stake,  and  on  the  stake  set  a staff  and  note  the 
height  cut  by  the  horizontal  wire,  then  take  the  same  distance 
from  the  instrument  in  an  opposite  direction,  and  drive  another 
stake. 

On  that  stake  set  the  staff  and  note  the  height  cut  by  the  wire 
when  the  telescope  is  turned  in  tliat  direction. 

The  difference  of  the  two  observations  is  evidently  the  differ- 
ence of  level  of  the  two  stakes. 

Set  the  instrument  over  the  lowest  stake,  or  that  upon  which 
the  greatest  height  was  indicated,  and  bring  the  levels  on  the 
plates  and  telescope  into  adjustment  as  at  first. 

Then,  with  the  staff  measure  the  perpendicular  distance  from 
the  top  of  the  stake  to  the  centre  of  the  eye-piece ; from  that 
distance  subtract  the  difference  of  level  between  the  two  stakes, 
and  mark  the  point  on  the  staff  thus  found  ; place  the  staff  on  the 
other  stake,  and  with  the  tangent  screw  bring  the  horizontal  wire 
to  the  mark  just  found,  and  the  line  will  be  level. 

The  telescope  now  being  level,  bring  tlie  bubble  of  the  level 
into  the  centre,  by  turning  the  little  nuts  at  the  ends  of  the  tube, 
and  noting  again  if  the  wires  cut  the  point  on  tlie  staff;  screw  up 
the  nuts  firmly  and  the  adjustment  will  be  completed. 

With  such  a level  carefully  adjusted,  the  engineer  by  taking 
equal  fore  and  back  sights,  can  run  horizontal  lines  with  great 
rapidity,  and  a good  degree  of  accuracy. 


THE  surveyors’  TRANSIT. 


63 


To  Use  the  Surveyors’  Transit. 

In  surveying  with  this  instrument,  the  plates  must  be  set  so 
that  the  zeros  of  the  circle  and  the  verniers  correspond,  and  firmly 
clamped  together,  the  south  end  of  the  compass  face  being  turned 
towards  the  eye  end  of  the  telescope  when  it  is  in  the  position 
shown  in  Fig.  11. 

The  surveyor  may  then  proceed  precisely  as  with  the  plain 
compass. 

To  Tukn  off  Angles. — When  angles  are  to  he  measured 
independently  of  the  needle,  proceed  precisely  as  directed  in  the 
description  of  the  Rail  Road  Compass. 

The  Variation  of  the  Needle  is  also  set  off  as  mentioned 
in  our  account  of  that  instrument. 

Sizes  of  the  Surveyors^  Transit. 

We  make  three  sizes  of  the  Surveyors’  Transit,  viz: 

The  4 inch  needle,  with  divided  horizontal  limb  of  6 inches, 

The  5 inch  needle,  with  limb  of  6|  inches,  and 

The  5|-  inch  needle,  with  limb  of  7 inches  diameter. 

They  are  all  used  with  the  light  adjusting  tripod  head  already 
mentioned. 

The  average  weights  of  the  three  sizes,  exclusive  of  the  tripod 
legs,  and  with  plain  telescopes,  are  respectively  as  follows  : 


4 inch  Needle, 12  lbs. 

5 inch  Needle, 13  lbs. 

5-J-  inch  Needle, 14  lbs. 


Merits  of  the  Surveyors'  Transit. 

In  this  instrument,  as  just  described,  the  surveyor  will  recog- 
nize advantages  not  possessed  by  any  other  instrument  with  which 
we  are  acquainted. 

Combining  the  capabilities  of  a needle  instrument,  with  a fine 
telescope,  and  the  accuracy  of  a divided  limb  and  verniers,  and 
having  also  the  means  for  turning  off  the  variation  of  the  needle, 
5^ 


54 


THE  surveyors’  TRANSIT. 


it  is  for  a mixed  practice  of  accurate  surveying  and  engineering, 
such  indeed  as  is  required  of  most  city  engineers,  the  best  instru- 
ment ever  constructed. 

The  arrangement  of  the  sockets  which  we  have  alluded  to  in 
our  account  of  the  Rail  Road  Compass,  is  very  perfect  and  stable, 
and  the  movement  of  the  plates  almost  entirely  free  from  friction. 

We  made  the  first  of  our  Surveyors’  Transits  about  three  years 
ago,  and,  from  that  time  to  this,  have  found  their  sale  continually 
increasing,  and  those  that  have  been  in  use  satisfying  invariably 
the  best  expectations  of  the  purchaser. 

The  peculiar  construction  of  the  sockets  and  plates  of  this  in- 
strument are  entirely  our  own  invention,  and  we  feel  the  utmost 
confidence  in  recommending  it  to  all  whose  practice  is  such  as  to 
require  the  use  of  the  needle  combined  with  that  of  the  divided 
circle  and  verniers. 


ENGINEERS’  INSTRUMENTS. 


THE  ENGINEERS’  TRANSIT. 

. Fig.  12. 


Having  now  described  the  various  instruments  emidoyed  in 
surveying,  we  sliall  consider  those  whose  use  belongs  more 
especially  to  the  practice  of  the  civil  engineer,  and  of  these  the  first 
in  importance  is  that  termed  the  Engineers’  Transit. 


56 


THE  ENGINEERS'  TRANSIT. 


It  differs  from  the  instrument  just  described  in  having  the  com- 
pass circle,  verniers  and  standards,  attached  to  the  same  plate, 
and  moving  together  above  the  divided  circle  or  limb. 

The  engraving  on  the  frontispiece  will  convey  a good  idea  of  our 
latest  improved  Engineers’  Transit,  and  to  this  the  reader  will  please 
refer  in  the  following  detailed  description  of  its  different  parts. 

The  Telescope  is  from  twelve  to  thirteen  inches  long,  and  is 
of  the  finest  quality. 

Like  all  those  of  our  own  instruments,  it  is  capable  of  reversion 
only  at  the  object  end,  though  we  liave  often,  when  desired,  made 
tlie  other  or  even  both  ends  to  reverse. 

The  rack  and  pinion  movement  of  the  object-glass  is  usually 
placed,  as  shown,  on  the  top  of  the  telescope  tube,  though  some- 
times on  the  side,  as  the  engineer  may  prefer. 

Pinion  to  Eye-Glass. — We  have  often  adapted  to  the  eye- 
piece of  this  and  our  other  Transits,  a rack  and  pinion  movement 
which  is  placed  on  the  side  of  the  tube,  and  is  very  excellent  in 
bringing  the  cross-wires  precisely  into  focus. 

The  Shade. — A short  piece  of  ihin  tube  called  a shade,  is 
always  made  to  accompany  this  and  the  previous  instrument,  and 
is  used  to  protect  the  object-glass  from  the  glare  of  the  sun,  or  from 
moisture  ; it  must  be  removed  whenever  the  telescope  is  reversed, 
unless  the  telescope  is  made  to  reverse  at  the  eye-end,  as  is  some- 
times desired. 

The  interior  construction  of  the  telescope  is  similar  to  those 
already  described. 

The  Standards  are  made  of  well  hammered  brass,  firm  and 
strong. 

On  one  of  tliem  will  be  seen  the  little  moveable  box  with  the 
capstan  head  screw  underneath,  by  which  the  cross-wires  are 
adjusted  to  trace  a vertical  line,  as  described  on  pages  35  and  36, 
in  our  account  of  the  Vernier  Transit. 

3'he  liiMii  or  dividf'd  circle  is  sevum  inches  in  diameter,  is  grad- 
uated to  half  d(;grees,  and  read  by  two  opposite  verniers  to  si^igle 
minutes. 


THE  ENGINEERS  TRANSIT. 


57 


The  Verniers  are  double,  reading  both  ways  from  the  centre, 
and  are  placed  on  the  sides  of  the  plate  at  right  angles  to  the 
telescope. 

The  Needle  is  five  inches  long,  and  is  raised  by  a milled  screw 
head  shown  in  tlie  cut,  placed,  above  the  plate. 

The  Clamp  and  Tangent  Screws  are  also  above,  so  as  to  be 
very  accessible,  and  out  of  the  reach  of  ordinary  accidents.  The 
clamping  of  tlie  limb  is  effected  in  the  interior,  the  aperture  being 
covered  with  a w^asher  to  exclude  the  dust  and  moisture. 

The  Levels,  as  shown  in  the  cut,  are  above ; they  are  both 
adjustable  witli  the  ordinary  steel  pin. 

The  glass  vials  used  in  the  levels  of  this  and  the  Surveyors' 
Transit,  are  ground  on  their  upper  interior  surface,  so  that  the 
bubble  moves  very  evenly  and  with  great  sensitiveness. 

The  Tripod  Head  of  this  instrument  is  made  considerably 
heavier  than  that  of  the  Surveyors’  Transit. 

The  upper  plate  is  about  five  inches  diameter,  made  thick  and 
of  well  hammered  brass ; into  this  are  screwed  the  long  nuts  or 
sockets  for  the  leveling  screws,  and  on  the  upper  surface  is  seen 
the  clamp,  with  the  two  butting  tangent  screws. 

With  these,  the  movement  is  made  very  slowly,  and  much 
more  firmly  than  is  possible  with  a single  tangent  screw. 

The  leveling  screws  are  of  bell  metal,  and  have  a broad  three 
milled  head ; they  rest  on  the  lower  plate,  in  the  little  cups  spoken 
of  in  our  account  of  the  previous  instrument. 

In  the  engraving  on  the  frontispiece  it  will  be  seen  that  the 
screws  are  entirely  covered  above  the  plate,  by  little  brass  covers 
w’hich  protect  the  threads  from  dust  and  corrosion. 

The  lower  plate  is  a little  smaller  than  the  upper,  milled  on  the 
edge,  and  made  to  connect  by  a screw,  with  the  tripod  legs. 

This  tripod  head  is  attached  to  the  sockets  of  the  limb  and 
vernier  plate,  and  is  removed  with  them,  when  the  instrument  is 
packed  in  the  box  for  transportation. 

The  loop  for  tlie  plurnb-bob  is  connected  by  a screw  to  the 


58 


THE  engineers’  TRANSIT. 


spindle  of  the  vernier  plate,  so  that  it  is  always  suspended  from 
the  exact  centre  of  the  instrument. 

The  A ttachments  of  the  Transit. 

The  wood  cut,  fig.  12,  shows  the  vertical  circle  of  four  and  a half 
inches  diameter,  which  is  read  by  a double  vernier  to  minutes, 
and  also  the  clamp  and  tangent  movement  to  the  axis  of  the 
telescope. 

These,  with  the  addition  of  a level  on  the  telescope,  are  often 
used  with  this  instrument,  though  the  majority  of  engineers  prefer 
an  instrument  with  plain  telescope,”  like  that  shown  on  frontis- 
piece, 

Microin&ter. 

It  is  sometimes  very  convenient  in  the  use  of  both  the  Transit 
and  Leveling  Instrument,  to  employ  some  simple  method  of  ascer- 
taining the  distances  of  objects  without  resorting  to  actual  meas- 
urements. 

This  is  well  effected  by  what  is  termed  ‘‘Micrometer,”  by  the 
French  called  “Stadia,”  placed  in  the  plane  of  the  cross-wires  in 
the  interior  of  the  telescope. 

In  those  we  have  sometimes  made,  two  horizontal  wires  are 
fastened  to  the  diaphragm,  at  such  a distance  apart  that  they  will 
just  include  a tenth  of  a foot  on  a rod  placed  one  hundred  feet 
distant. 

When  nicely  adjusted  to  this  interval  they  will  cover  two-tenths 
at  two  hundred  feet;  three,  at  three  hundred,  and  in  the  same 
proportion  for  any  intermediate  or  greater  distance. 

In  this  manner  the  engineer  can  estimate  the  distances  of  his 
assistants  with  surprising  accuracy,  and  by  a simple  observation. 

To  adjust  the  Transit. 

The  adjustment  of  tins  instrument  and  its  attaclimcnts  have 
been  described  in  our  account  of  those  previously  considered. 


THE  engineers’  TRANSIT. 


59 


To  use  the  Engineers'  Transit. 

But  little  need  be  added  to  what  lias  been  already  given  in  the 
previous  pages. 

The  Needle  is  of  service  principally  as  a rough  check  upon 
the  readings  of  the  verniers  in  the  measurment  of  horizontal 
angles,  any  glaring  mistake  being  detected,  by  noticing  the  angles 
indicated  by  both,  in  the  different  positions  of  the  telescope. 

It  may  also  be  used  as  in  the  compass,  to  give  the  direction  in 
which  the  lines  are  run,  but  its  employment  is  only  subsidiary  to 
the  general  purposes  of  the  Transit. 

Sizes  of  the  Trail  sit. 

"We  make  two  different  sizes  of  this  instrument,  viz: 

The  Five  Inch  Transit  just  described,  which,  exclusive  of 
the  tripod  legs,  weighs  about  13-J-  lbs.,  and  the 

Four  Inch  Transit,  precisely  similar  in  style,  but  about  one- 
fourth  smaller  and  lighter  in  all  its  parts. 

It  has  a telescope  of  about  ten  inches  long,  a four  inch  needle, 
and  a divided  limb  of  six  inches  diameter. 

Weight  of  the  Attachments. 

As  it  may  sometimes  be  desirable  to  know  the  weights  of  the 
different  extras  or  attachments,  often  used  in  this  and  the  other 
Transits  previously  described,  we  here  add  them  in  detail. 

Ground  level  tube,  with  vial  complete, . . . . 7-J-  oz. 


Vertical  circle,  with  vernier, 6 oz. 

Clamp  and  Tangent  to  axis, 4 oz. 


Besides  the  simple  form  of  the  Engineers’  Transit,  we  also 
make  important  modifications,  which  may  be  desired  by  the  engi- 
neer; a few  of  these  we  shall  now  enumerate. 

The  Watch  Telescope. 

A telescope  is  sometimes  attached  to  a socket,  moving  in  a hol- 
low cylinder  which  surrounds  the  lengthened  socket  of  the  limb, 
and  is  thus  capable  of  moving  around  under  the  plates,  and  of  a 
short  vertical  motion. 


60 


THE  ENGINEERS  TRANSIT. 


The  cylinder  which  supports  it,  may  be  clamped  firmly  to  the 
limb,  and  the  wires  of  the  telescope  tlius  fixed  upon  any  object, 
by  the  tangent  movement  of  the  tripod  head. 

The  object  of  the  watch  telescope,  is  to  guard  against,  and  de- 
tect any  inaccuracy  arising  from  the  disturbance  of  the  limb,  dur- 
ing the  progress  of  an  observation,  or  the  measurement  of  angles. 

Thus,  if  the  wires  of  both  telescopes  are  fixed  upon  the  same 
object,  and  the  w'atch  telescope  kept  still  upon  it,  while  the  ver- 
nier plate  is  undamped,  and  the  upper  telescope  shifted  to  the 
second  point,  a reference  to  the  watch  telescope  will  immediately 
betray  any  disturbance  in  the  position  of  the  limb. 

But,  in  spite  of  its  excellencies  in  cases  where  great  nicety  is 
required,  the  additional  weight  and  complication  of  the  watch 
telescope,  have  caused  it  to  be  regarded  by  most  American  engi- 
neers as  an  encumbrance,  rather  than  an  advantage  to  the  Transit. 

21ie  Theodolite  Axis. 

In  place  of  the  ordinary  axis  of  the  telescope  repre^'ented  in 
our  engraving,  we  sometimes  make  one  resembling  the  Y axis  of 
the  English  Theodolite. 

This  modification  is  desirable,  in  cases  where  this  instrument  is 
intended  to  subserve  llie  purposes  of  both  level  and  transit. 

In  such  an  arrangemeiit,  the  telescope  is  confined  in  the  axis 
with  clips,  by  loosening  which,  it  may  be  revolved  in  tlie  wyes, 
or  taken  out  and  reversed  end  for  end,  precisely  like  that  of  the 
leveling  instrument. 

The  standards  also  allow  its  transit,  or  complete  revolution  in 
a vertical  direction. 

In  such  an  instrument,  the  adjustment  of  the  wires,  and  level 
of  the  telescope,  is  effected  in  the  same  manner  as  those  of  the 
leveling  instrument,  the  tangent  movement  of  the  axis  serving, 
instead  of  the  leveling  screws,  to  bring  the  bubble  and  wires  into 
position. 

With  this  modification  of  the  transit,  wc  have  also  frequently 
added,  that  of  a small  level  bar,  wyes,  &c.,  into  which  the  tele- 


THE  engineers’  TRANSIT. 


61 


scope  may  be  transferred,  making  thus  a miniature  leveling 
instrument. 

This  may  be  placed  upon  the  socket  and  tripod  head  of  the 
transit,  and  made  capable  of  taking  levels  with  a good  degree  of 
accuracy. 

When  ^desirable,  a vertical  wheel  may  be  placed  on  the  axis  of 
the  telescope  of  this  instrument,  and  thus  all  the  properties  of  the 
English  Theodolite,  united  with  those  of  the  American  Transit. 

T'wo  Telescope  Instruments. 

We  have  occasionally  manufactured  instruments  provided  with 
two  telescopes,  having  their  centres  in  the  same  vertical  line,  and 
one  above  the  other. 

The  upper  telescope  has  a range  of  about  35^^  each  way,  in  a 
vertical  direction,  and  like  that  of  the  Engineers’  Transit,  is  car- 
ried on  a vernier  plate,  furnished  with  levels,  needle  and  tangent 
movement,  and  reading  to  minutes  on  the  horizontal  limb  ; the 
lower  one  is  placed  in  the  centre  of  the  expanded  vertical  axis  of 
the  limb,  by  which  it  is  moved  horizontally  ; and  it  has  also  a 
range  of  about  20°  each  way  in  a vertical  direction. 

When  the  line  of  collimation  of  both  telescopes  is  fixed  upon 
the  same  object,*  the  zeros  of  the  vernier  and  limb  are  in  coinci- 
dence, and  when  the  vernier  plate  is  turned  180  degrees  the 
wires  of  the  telescopes  will  cut  the  extremities  of  a straight  line, 
in  one  point  of  which,  the  centre  of  the  instrument  is  placed. 

In  the  same  manner,  it  is  manifest  that  any  angle  may  be  laid 
off  on  the  limb,  and  the  points  be  indicated  by  the  wires  of  both 
telescopes,  without  changing  the  position  of  the  limb. 

The  lower  telescope  may  also  be  used  as  a guard  or  watch,  to 
detect  any  disturbance  in  the  instrument  during  the  time  of  an 
observation. 


C 


TW'EKTT  INCH  TELESCOPE. 
Fig.  13. 


THE  LEVELING  INSTRUMENT. 


Of  the  different  varieties  of  the  Leveling  Instrument,  that 
termed  the  Y Level,  has  been  almost  universally  preferred  by 
American  engineers,  on  account  of  the  facility  of  its  adjustment, 
and  superior  accuracy. 

Of  these  Levels  we  manufacture  four  different  sizes,  having 
telescopes  of  sixteen,  eighteen,  twenty,  and  twenty-two  inches 
long,  respectively. 

The  cut  on  the  opposite  page  represents  our  twenty  inch  Level; 
that  of  the  sixteen  inch  telescope  will  be  shown  beyond. 

We  shall  consider  the  several  parts  of  the  instrument  in  detail: 

The  Telescope  has  at  each  end  a ring  of  bell-metal,  turned 
very  truly  and  both  of  exactly  the  same  diameter ; by  these  it 
revolves  in  the  wyes,  or  can  be  at  pleasure  clamped  in  any  posi- 
tion when  the  clips  of  the  wyes  are  brought  down  upon  the 
rings,  by  pushing  in  the  tapering  pins. 

The  telescope  has  a rack  and  pinion  movement  to  both  object  • 
and  eye-glasses,  an  adjustment  for  centering  the  eye-piece,  shown 
at  A A,  in  the  longitudinal  section  of  the  telescope,  (page  64,) 
and  another  seen  at  C C,  for  ensuring  the  accurate  projection  of 
the  object-glass,  in  a straight  line. 

Both  of  these  are  completely  concealed  from  observation  and 
disturbance,  by  a thin  ring  which  slides  over  them. 

The  telescope  has  also  a shade  over  the  ol)ject-glass,  so  made, 
that  whilst  it  may  be  readily  moved  on  its  slide  over  the  glass,  it 
cannot  be  dropped  off  and  lost. 

The  shade  of  our  sixteen  inch  level,  is  made  to  take  off,  like 
that  of  the  Engineers’  Transit, 


64 


THE  LEVELING  INSTRUMENT. 


The  interior  construction  of  the  telescope 
will  be  readily  understood  from  fig.  14,  which 
represents  a longitudinal  section,  and  exhibits  I 
the  adjustment  which  ensures  the  accurate  pro- 
jection of  the  object-glass  slide. 

As  this  is  peculiar  to  our  instruments,  and 
is  always  made  by  the  maker  so  permanently 
as  to  need  no  further  attention  at  the  hands  of 
the  engineer,  we  shall  here- describe  the  means 
by  which  it  is  effected,  somewhat  in  detail. 

The  necessity  for  such  an  adjustment  will 
appear,  when  we  state,  that  it  is  almost  impos- 
sible to  make  a telescope  tube  so  that  it  shall  be 
perfectly  straight  on  its  interior  surface. 

Such  being  the  case,  it  is  evident  that  the 
object-glass  slide  which  is  fitted  to  this  surface, 
and  moves  in  it,  must  partake  of  its  irregularity,  ^ 
so  that  the  glass  and  the  line  of  collimation  . 
depending  upon  it,  though  adjusted  in  one  posi-  ^ 
tion  of  the  slide,  will  be  thrown  out  when  the 
slide  is  moved  to  a different  point. 

To  prove  tliis,  let  any  level  be  selected  which 
is  constructed  in  the  usual  manner,  and  the  line  ^ 
of  collimation  adjusted  upon  an  object  taken  as 
near  as  the  range  of  the  slide  will  allow ; then 
let  another  be  selected,  as  distant  as  may  be 
clearly  seen ; upon  this  revolve  the  wires,  and 
they  will  almost  invariably  be  found  out  of 
adjustment,  sometimes  to  an  amount  fatal  to 
any  confidence  in  the  accuracy  of  the  instrument. 

The  arrangement  adopted  by  us  to  correct  this 
imperfection,  and  which  so  perfectly  accomplish- 
es its  [)urposos,  is  shown  in  the  adjoining  cut, 
fig.  14. 


THE  LEVELING  INSTRUMENT. 


65 


Here  are  seen  the  two  bearings  of  the  object-glass  slide,  one 
being  in  the  narrow  bell  metal  ring  which  slightly  contracts  the 
diameter  of  the  main  tube,  the  other  in  the  small  adjustable  ring, 
also  of  bell  metal,  shown  at  C C,  and  suspended  by  four  screw^s  in 
the  middle  of  the  telescope. 

Advantage  is  here  taken  of  the  fact,  that  the  rays  of  light  are 
converged  by  the  object-glass,  so  that  none  are  obstructed  by  the 
contraction  of  the  slide,  except  those  which  diverge,  and  which 
ought  always  to  be  intercepted,  and  absorbed  in  the  blackened 
surface  of  the  interior  of  the  slide. 

Now,  in  such  a telescope,  the  perfection  of  movement  of  the 
slide,  depends  entirely  upon  its  exterior  surface,  at  the  points  of 
the  two  bearings. 

These  surfaces  are  easily  and  accurately  turned  concentric,  and 
parallel  witli  each  other  and  being  fitted  to  the  rings,  it  only  re- 
mains necessary  to  adjust  the  position  of  the  smaller  ring,  so  that 
its  centre  will  coincide  with  that  of  the  optical  axis  of  the  object 
glass. 

When  this  has  been  once  well  done,  no  further  correction  will 
be  necessary,  unless  the  telescope  should  be  seriously  injured. 

The  manner  in  which  the  adjustment  of  the  object-glass  slide  is 
effected  will  be  considered  when  we  come  to  speak  of  the  other 
adjustments. 

Eack  and  Pinion. — As  seen  in  fig.  13,  our  Level  telescopes 
are  usually  furnished  with  the  ordinary  rack  and  pinion  movement 
to  both  object  and  eye  tubes. 

The  advantages  of  an  eye  piece  pinion,  are,  that  the  eye-piece 
can  be  shifted  without  danger  of  disturbing  the  telescope,  and  that 
the  wires  are  more  certainly  brought  into  distinct  view,  so  as  to 
avoid  effectually  any  error  pf  observation,  arising  from  what  is 
termed  the  instrumental  paiallax. 

The  position  of  the  pinion  on  the  tube  is  varied  in  different  in- 
struments according  to  the  choice  of  the  engineer. 

We  usually  place  our  object  slide  pinion  on  tlie  top  of  Transit 


66 


THE  LEVELING-  INSTRUMENT. 


telescopes,  and  on  the  side  of  those  of  the  Level.  The  pinion  of 
the  eye  tube,  is  always  placed  on  the  side  of  the  telescope. 

The  Level  or  ground  bubble  tube  is  attached  to  the  under  side 
of  the  telescope,  and  furnished  at  the  different  ends  with  tlie  usual 
movements,  in  both  horizontal  and  vertical  directions. 

The  aperture  of  the  tube,  through  which  the  glass  vial  appears, 
is  about  five  and  one-fourth  inches  long,  being  crossed  at  the  cen- 
tre by  a small  rib  or  bridge,  which  greatly  strengthens  the  tube. 

The  level  scale  which  extends  over  the  whole  length,  is  gradu- 
ated into  spaces  a little  coarser  than  tenths  of  an  inch,  and  fig- 
ured at  every  fifth  division,  counting  from  zero  at  the  centre  of 
the  bridge  ; the  scale  is  set  close  to  the  glass. 

The  bubble  vial  is  made  of  thick  glass  tube,  selected  so  as  to 
have  an  even  bore  from  end  to  end,  and  finely  ground  on  its  upper 
interior  surface,  that  the  run  of  the  air  bubble  may  be  uniform 
throughout  its  whole  range. 

The  sensitiveness  of  a ground  level,  is  determined  best  by  an 
instrument  called  a level  tester,  having  at  one  end  two  Y’s  to  hold 
the  tube,  and  at  the  other  a micrometer  wheel  divided  into  hun- 
dredths, and  attached  to  the  top  of  a fine  threaded  screw  which 
raises  the  end  of  the  tester  very  gradually. 

The  number  of  divisions  passed  over  on  the  perimeter  of  the 
wheel,  in  carrying  tlie  bubble  over  a tenth  of  the  scale,  is  the  in- 
dex of  the  delicacy  of  the  level.  In  the  tester  which  we  use,  a 
movement  of  the  wheel  ten  divisions,  to  one  of  the  scale,  indicates 
the  degree  of  delicacy  generally  preferred  for  rail  road  engineering. 

For  canal  work  practice,  a more  sensitive  bubble  is  often  de- 
sired, as  for  instance,  one  of  seven  or  eight  divisions  of  the  wheel, 
to  one  of  the  scale. 

The  Wyes  of  our  levels  are  made  large  and  strong,  of  the 
best  bell  metal,  and  each  have  two  nuts,  both  being  adjustable 
with  the  ordinary  steel  pin. 

Tfie  clips  are  brought  down  on  the  rings  of  the  telescope  tube 


THE  LEVELING  INSTRUMENT. 


67 


by  the  Y pins,  which  are  made  tapering,  so  as  to  clamp  the  rings 
very  firmly. 

The  Level  Bar  is  made  round,  of  well  hammered  brass,  and 
shaped,  so  as  to  possess  the  greatest  strength  in  the  parts  most 
subject  to  sudden  strains. 

Connected  with  the  level  bar  is  the  head  of  the  tripod  socket. 

The  Tripod  Socket  is  compound  ; the  interior  spindle,  upon 
which  the  whole  instrument  is  supported,  is  made  of  steel,  and 
nicely  ground,  so  as  to  turn  evenly  and  firmly,  in  a hollow  cylinder 
of  bell  metal ; this  again,  has  its  exterior  surface,  fitted  and  ground 
to  the  main  socket  of  the  tripod  head. 

The  bronze  cylinder  is  held  upon  the  spindle  by  a washer  and 
screw,  the  head  of  this  having  a hole  in  its  centre,  through  which __ 
the  string  of  the  plumb  bob  is  passed. 

The  upper  part  of  the  instrument,  with  the  socket,  may  thus  be 
detached  from  the  tripod  head  ; and  this,  also,  as  in  the  case  of  all 
our  instruments,  can  be  unscrewed  from  the  legs,  so  that  both 
may  be  conveniently  packed  in  the  box. 

A little  under  the  upper  parallel  plate  of  the  tripod  head,  and  in 
the  main  socket,  is  a screw  which  can  be  moved  into  a correspond- 
ing crease,  turned  on  the  outside  of  the  hollow  cjdinder,  and  thus 
made  to  hold  the  instrument  in  tlie  tripod,  when  it  is  carried  upon 
the  shoulders. 

It  will  be  seen  from  tlie  cut,  that  the  arrangement  just  described 
allows  long  sockets,  and  yet  brings  the  whole  instrument  down  as 
closely  as  possible  to  the  tripod  head,  both  objects  of  great  impor- 
tance in  the  construction  of  any  instrument. 

The  Tripod  Head  has  the  same  plates  and  leveling  screws, 
as  that  described  in  the  account  of  the  Engineers’  Transit ; the 
tangent  screw,  however,  is  commonly  single. 

For  our  sixteen  inch  level  we  make  a smaller  tripod  head,  re- 
sembling that  used  with  the  lighter  engineer’s  transit. 


SIXTEEN  INCH  TELESCOPE. 
Fig.  15 


THE  LEVELING-  INSTRUMENT. 


69 


The  Adjustments. 

Having  now  completed  the  description  of  the  different  parts  of 
the  Leveling  Instrument,  we  are  ready  to  proceed  with  their 
adjustment,  and  shall  begin  with  that  of  the  object-slide,  which, 
although  always  made  by  the  maker,  so  permanently  as  to  need 
no  further  attention  at  the  hands  of  the  engineer,  unless  in  cases 
of  derangement  by  accident,  is  yet  peculiar  to  our  instruments 
and  therefore  not  familiar  to  many  en<rineers. 

To  Adjust  the  Object  Slide. — The  maker  selects  an  object 
as  distant  as  may  be  distinctly  observed,  and  upon  it  adjusts  the 
line  of  collimation,  in  the  manner  hereafter  described,  making  the 
centre  of  the  wires  to  revolve  without  passing  either  above  or 
below  the  point  or  line  assumed. 

In  this  position,  the  slide  will  be  drawn  in  nearly  as  far  as  the 
telescope  tube  will  allow. 

He  then,  with  the  pinion  head,  moves  out  the  slide  until  an 
object,'  distant  about  ten  or  fifteen  feet,  is  brought  clearly  in  view  ; 
again  revolving  the  telescope  in  the  Ys,  he  observes  whether  the 
wires  will  reverse  upon  this  second  object. 

Should  this  happen  to  be  the  case,  he  will  assume,  that  as  the 
line  of  collimation  is  in  adjustment  for  these  two  distances,  it  will 
be  so  for  all  intermediate  ones,  since  the  bearings  of  the  slide  are 
supposed  to  be  true,  and  their  planes  parallel  with  each  other. 

If,  however,  as  is  most  probable,  either  or  both  wires  fiiil  to  re- 
verse upon  the  second  point,  he  must  then,  by  estim.ation,  remove 
half  the  error  by  the  screws  C C,  (fig.  14,)  at  right  angles  to  the  hair 
sought  to  be  corrected,  remembering  at  the  same  time,  that  on  ac- 
count of  the  inversion  of  the  eye-piece,  he  must  move  the  slide  in 
the  direction  which  apparently  increas'es  the  error.  When  both 
wires  have  thus  been  treated  in  succession,  the  line  of  collimation 
is  adjusted  on  the  near  object,  and  the  telescope  again  brought 
upon  the  most  distant  point;  liere  the  tube  is  again  revolved,  tho 
reversion  of  the  wires  upon  the  object  once  more  tested,  and  tho 
correction,  if  necessary,  made  in  precisely  the  same  manner. 


70 


THE  LEVELING  INSTRUMENT. 


He  proceeds  thus,  until  the  wires  will  reverse  upon  both  objects 
in  succession  ; the  line  of  collimation  will  then  be  in  adjustment 
at  these,  and  all  intermediate  points,  and  bj  bringing  the  screw 
heads,  in  the  course  of  the  operation,  to  a firm  bearing  upon  the 
washers  beneath  them,  the  adjustable  ring  will  be  fastened  so  as 
for  many  years  to  need  no  further  adjustment. 

When  this  has  been  completed,  the  tliin  brass  ferule  is  slipped 
over  the  outside  ring,  concealing  the  screw  heads,  and  avoiding 
the  danger  of  their  disturbance  by  an  inexperienced  operator. 

In  effecting  this  adjustment  it  is  always  best  to  bring  the  wires 
into  the  centre  of  the  field  of  view,  by  moving  the  little  screws 
A A,  (fig.  14,)  working  in  the  ring  which  embraces  the  eye-piece 
tube. 

Should  the  engineer  desire  to  make  this  adjustment,  it  will  be 
necessary  to  remove  the  bubble  tube,  in  order  that  the  small  screw 
immediately  above  its  scale  may  be  operated  upon  with  the  screw 
driver. 

The  adjustment  we  have  now  given  is  preparatory  to  those 
which  follow,  and  are  common  to  all  leveling  instruments  of 
recent  construction,  and  are  all  that  the  engineer  will  have  to  do 
with  in  using  our  own  instruments.  What  is  still  necessary 
then  is — 

1.  To  adjust  the  line  of  collimation^  or  in  other  words,  to  bring 
both  wires  into  the  optical  axis,  so  that  their  point  of  intersection 
will  remain  on  any  given  point,  during  an  entire  revolution  of  the 
telescope. 

2.  T'o  bring  the  level  bitbhle  parallel  with  the  bearings  of  the  Y 
rings,  and  with  the  longitudinal  axis  of  the  telescope. 

?).  To  adjust  the  wyes^  or  to  bring  the  bubble  into  a position  at 
riglit  angles  to  tlie  vertical  axis  of  the  instrument. 

To  Adjust  thk  Line  of  Collimation,  set  the  tripod  firmly, 
remove  the  Y pins  from  the  clips,  so  as  to  allow  the  telescope  to 
turn  freely,  clamp  the  instrument  to  the  tripod  head,  and  by  the 
leveling  and  tangent  screws,  bring  either  of  the  wires  upon  a 


THE  LEVELING  INSTRUMENT. 


71 


clearly  marked  edge  of  some  object,  distant  from  one  to  five 
hundred  feet. 

Then  with  the  hand  carefully  turn  the  telescope  half  way  around, 
so  that  the  same  wire  is  compared  with  the  object  assumed. 

Should  it  be  found  above  or  below,  bring  it  half  way  back  by 
moving  the  capstan  head  screw's  at  right  angles  to  it,  remember- 
ing always  the  inverting  property’  of  the  eye-piece  ; now  bring 
the  wire  again  upon  the  object  and  repeat  the  first  operation  until 
it  wull  reverse  correctly. 

Proceed  in  the  same  manner  with  the  other  wire  until  the  ad- 
justment is  completed. 

Should  both  wires  be  much  out  it  will  be  well  to  bring  them 
nearly  correct  before  either  is  entirely  adjusted. 

When  this  is  effected,  slip  off  the  covering  of  the  eye-piece 
centering  screws,  shown  in  the  sectional  view  (fig.  14)  at  A A, 
and  move  each  pair  in  succession  with  a small  screw  driver,  until 
the  wnres  are  brought  into  the  centre  of  the  field  of  view^ 

The  inversion  of  the  eye-piece  does  not  effect  this  operation, 
and  the  screws  are  moved  direct. 

To  test  the  correctness  of  the  centering,  revolve  the  telescope, 
and  observe  w’h ether  it  appears  to  shift  the  position  of  an  object. 

Should  any  movement  be  perceived,  the  centering  is  not  per- 
fectly effected. 

It  may  here  be  repeated,  that  in  all  telescopes  the  position  and 
adjustment  of  the  line  of  collimation  depends  upon  that  of  the 
object-glass ; and  therefore,  that  the  movement  of  the  eye-piece 
does  not  affect  the  adjustment  of  the  wires  in  any  respect. 

When  the  centering  has  been  once  effected  it  remains  perma- 
nent, the  cover  being  slipped  over  to  conceal  and  protect  it  from 
derangement  at  the  hands  of  the  curious,  or  inexperienced 
operator. 

To  Adjust  the  Level  Bubble. — Clamp  the  instrument  over 
either  pair  of  leveling  screws,  and  bring  the  bubble  into  the  centre 
of  the  tube. 


72 


THE  LEVELING  INSTRUMENT. 


Now  turn  the  telescope  in  the  wyes,  so  as  to  bring  the  level 
tube  on  either  side  of  the  centre  of  the  bar.  Should  the  bubble 
run  to  the  end  it  would  show  that  the  vertical  plane,  passing 
through  the  centre  of  the  bubble,  was  not  parallel  to  that  drawn 
through  the  axis  of  the  telescope  rings. 

To  rectify  the  error,  bring  it  by  estimation  half  way  back,  with 
the  capstan  head  screws,  which  are  set  in  either  side  of  the  level 
holder,  placed  usually  at  the  object  end  of  the  tube. 

Again,  bring  the  level  tube  over  the  centre  of  the  bar,  and  ad- 
just the  bubble  in  the  centre,  turn  the  level  to  either  side,  and,  if 
necessary,  repeat  the  correction  until  the  bubble  will  keep  its  posi- 
tion, when  the  tube  is  turned  half  an  inch  or  more,  to  either  side 
of  the  centre  of  the  bar. 

The  necessity  for  this  operation  arises  from  the  fact,  that  when 
the  telescope  is  reversed  end  for  end  in  the  wyes  in  the  other  and 
principal  adjustment  of  the  bubble,  we  are  not  certain  of  placing 
the  level  tube  in  the  same  vertical  plane,  and,  therefore,  it  would 
be  almost  impossible  to  effect  the  adjustment  without  a lateral 
correction. 

Having  now,  in  great  measure,  removed  the  preparatory  diffi- 
culties, we  proceed  to  make  the  level  tube  parallel  with  the 
bearings  of  the  Y rings. 

To  do  this,  bring  the  bubble  into  the  centre  with  the  leveling 
screws,  and  then  without  jarring  the  instrument,  take  the  telescope 
out  of  the  wyes  and  reverse  it  end  for  end.  Should  the  bubble 
run  to  either  end,  lower  that  eiid,  or  what  is  equivalent,  raise  the 
other  by  turning  the  small  adjusting  nuts,  on  one  end  of  the  level, 
until  by  estimation  half  the  correction  is  made  ; again  bring  the 
bubble  into  the  centre  and  repeat  tlie  whole  operation,  until  the 
reversion  can  be  made  without  causing  any  change  in  the  bubble. 

It  would  be  well  to  test  tlic  lateral  adjustment,  and  make  such 
correction  as  may  be  necessary  in  that,  before  the  horizontal 
adjustment  is  entirely  completed. 


THE  LEVELING  INSTEUMENT. 


73 


To  Adjust  the  'Wyes. — Having  effected  the  previous  adjust- 
ments, it  remains  now  to  describe  that  of  the  wjes,  or,  more  pre- 
cisely, that  which  brings  the  level  into  a position  at  right  angles, 
to  the  vertical  axis,  so  that  the  bubble  wall  remain  in  the  centre 
during  an  entire  revolution  of  the  instrument. 

To  do  this,  bring  the  level  tube  directly  over  the  centre  of  the 
bar,  and  clamp  the  telescope  firmly  in  the  wyes,  placing  it  as 
before,  over  two  of  the  leveling  screws,  unclamp  the  socket,  level 
the  bubble,  and  turn  the  instrument  half  way  round,  so  that  the 
level  bar  may  occupy  the  same  position  with  respect  to  the  level- 
ing screws  beneath. 

Should  the  bubble  run  to  either  end,  bring  it  half  way  back  by 
the  Y nuts  on  either  end  of  the  bar ; now  move  the  telescope 
over  the  other  set  of  leveling  screws,  bring  the  bubble  again  into 
the  centre  and  proceed  precisely  as  above  described,  changing  to 
each  pair  of  screws,  successively,  until  the  adjustment  is  very 
nearly  perfected,  when  it  may  be  completed  over  a single  pair. 

The  object  of  this  approximate  adjustment,  is  to  bring  the  upper 
parallel  plate  of  the  tripod  head  into  a position  as  nearly  horizon- 
tal as  possible,  in  order  that  no  essential  error  may  arise,  in  case 
the  level,  when  reversed,  is  not  brought  precisely  to  its  former 
situation.  When  the  level  has  been  thus  completely  adjusted,  if 
the  instrument  is  properly  made,  and  the  sockets  well  fitted  to  each 
other,  and  the  tripod  head,  the  bubble  will  reverse  over  each  pair 
of  screws  and  in  any  position. 

Should  the  engineer  be  unable  to  make  it  perform  correctly,  he 
should  examine  the  outside  socket  carefully  to  see  that  it  sets 
securely  in  the  main  socket,  and  also  notice  that  the  clamp  does 
not  bear  upon  the  ring  which  it  encircles. 

When  these  are  correct,  and  the  error  still  is  manifested,  it 
will,  probably,  be  in  the  imperfection  of  the  interior  spindle. 

After  the  adjustments  of  the  level  have  been  effected,  and  the 
bubble  remains  in  the  centre,  in  any  position  of  the  socket,  the 
engineer  should  carefully  turn  the  telescope  in  the  wyes,  and 
7 


74 


THE  LEVELING  INSTRUMENT. 


sighting  upon  the  end  of  the  level,  which  has  the  horizontal 
adjustment  along  each  side  of  the  wye,  make  the  tube  as  nearly 
vertical  as  possible. 

When  this  has  been  secured,  he  may  observe,  through  the 
telescope,  the  vertical  edge  of  a building,  noticing  if  the  vertical 
hair  is  parallel  to  it ; if  not,  he  should  loosen  two  of  the  cross- 
wire screws  at  right  angles  to  each  other,  and  with  the  hand  on 
these,  turn  the  ring  inside,  until  the  hair  is  made  vertical;  the 
line  of  collimation  must  then  be  corrected  again,  and  the  adjust- 
ments of  the  level  will  be  complete. 

To  use  the  Level. 

When  using  the  instrument  the  legs  must  be  set  firmly  into 
the  ground,  and  neither  the  hands  nor  person  of  the  operator  be 
allowed  to  touch  them,  the  bubble  should  then  be  brought  over 
each  pair  of  leveling  screws  successively,  and  leveled  in  each 
position,  any  corrections  being  made  in  the  adjustments  that  may 
appear  necessarj^ 

Care  should  be  taken  to  bring  the  wires  precisely  in  focus,  and 
the  object  distinctly  in  view,  so  that  all  errors  of  parallax  may  be 
avoided. 

This  error  is  seen  w^hen  the  eye  of  an  observer  is  moved  to 
either  side  of  the  centre  of  the  eye-piece  of  a telescope,  in  which 
the  foci  of  the  object  and  eye-glasses,  are  not  brought  precisely 
upon  the  cross-wires  and  object;  in  such  a case,  the  wires  will 
appear  to  move  over  the  surface,  and  the  observation  will  be 
liable  to  inaccuracy. 

In  all  instances  the  wires  and  object,  should  be  brought  into 
view  so  perfectly,  that  the  spider  lines  will  appear  to  be  fastened 
to  the  surface,  and  will  remain  in  that  position  however  the  eye 
is  moved. 

If  the  socket  of  the  instrument  becomes  so  firmly  set  in  the 
tri[)od  iKjad  as  to  be  difficult  of  removal  in  the  ordinary  way,  the 
cngin(;er  should  place  tlie  palm  of  his  hands  under  the  wye  nuts 


THE  LEVELING  INSTRUMENT. 


75 


at  each  end  of  the  bar  and  give  a sudden  upward  shock  to  the 
bar,  taking  care  also  to  hold  his  hands  so  as  to  grasp  it  the  mo- 
ment it  is  free. 

Weight  of  Leveling  Instrument 

The  average  weight  of  the  different  sizes  of  Levels,  exclusive 
of  the  tripod  legs,  are  as  follows : 


1 6 inch  Telescope, 11^  lbs, 

18  12 

20  “ 12|-  '' 

22  “ -.^13 


The  Farm  Level, 

Besides  the  various  engineers  levels,  we  make  a smaller  and 
cheaper  instrument,  styled  the  Farm  Level,  for  laying  out  mill 
seats,  draining  lands,  and  such  other  purposes  as  will  readily  oc- 
cur to  the  intelligent  agriculturist. 

This  instrument  has  a telescope  of  from  fourteen  to  sixteen 
inches  long,  with  Y and  bubble  adjustments  and  leveling  tripod, 
like  one  of  the  larger  instruments. 

The  tripod  head  is  made  like  that  figured  in  the  cut  of  the 
Surveyors’  Transit,  but  is  usually  without  tlie  clamp  and  tangent 
movement. 

There  is,  however,  a clamp  screw  on  the  side  of  the  socket  by 
which  it  may  be  held  on  the  spindle,  while  the  adjustments  are 
being  perfected. 

Builders'  Level. 

We  have  also  made  several  small  levels  for  Masons  use,  similar 
to  that  just  described,  but  generally  more  perfect  and  expensive, 

These  instruments  have  been  found  extremely  serviceable  in 
the  construction  of  extensive  buildings,  on  account  of  the  facility 
with  which  level  points  may  be  determined  on  every  side,  by  the 
simple  revolution  of  the  telescope, 


LEVELING  RODS. 


The  two  kinds  most  generallj  used  by  American  engineers,  are 
both  sliding  rods,  divided  into  hundredths  of  a foot  and  reading 
by  verniers  to  thousandths. 

Boston  Rod. 

That  known  as  the  Boston  or  Yankee  Rod,  is  formed  of  two 
pieces  of  light  bay  wood  or  mahogany,  each  about  six  and  a half 
feet  long,  connected  together  by  a tongue,  and  sliding  easily  by 
each  other,  in  both  directions. 

One  side  is  furnished  with  a clamp  sci:ew  and  vernier  at  each 
end,  the  other  carries  the  divisions,  marked  on  strips  of  satin  wood, 
inlaid  on  either  side. 

The  target  is  a rectangle  of  wood,  fastened  near  one  end  of  the 
divided  side,  and  having  its  horizontal  line  just  three-tenths  from 
the  extremity. 

The  target  being  fixed,  when  any  height  is  taken  above  six 
feet,  the  rod  is  changed  end  for  end,  and  the  divisions  read  by 
the  other  vernier  ; the  height  to  which  the  rod  can  be  extended, 
being  a little  over  eleven  feet. 

This  kind  of  rod  is  very  convenient  from  its  great  lightness,  but 
the  parts  are  made  too  frail  to  endure  the  rough  usage  of  this 
country,  and,  therefore,  American  engineers  have  generally  given 
the  preference  to  another,  made  lieavier  and  more  substantial. 

The  New  York  Rod. 

This  rod,  whicli  is  shown  in  the  engraving,  as  cut  in  two,  so 
tliat  the  ends  may  be  e.\hil)ited,  is  made  of  satin  wood,  in  two 
pieces  like  tlie  former,  but  sliding  one  from  the  other,  the  same 
end  being  always  held  on  the  ground,  and  the  graduations  starting 
from  that  point. 


LEVELING  RODS. 


77 


The  graduations  are  made  to  tenths  and  hun- 
dredths of  a foot,  the  tenth  figures  being  black, 
and  the  feet  marked  with  a large  red  figure. 

The  front  surface,  on  which  the  target  moves, 
reads  to  six  and  a half  feet;  when  a greater 
height  is  required,  the  horizontal  line  of  the  tar- 
get is  fixed  at  that  point,  and  the  upper  half  of 
the  rod,  carrying  the  target,  is  moved  out  of  the 
lower,  the  reading  being  now  obtained  by  a ver- 
nier on  the  graduated  side,  up  to  an  elevation  of 
twelve  feet. 

The  mountings  of  this  rod  are  differently  made 
by  different  manufacturers.  'W e shall  give  those 
which  we  have  adopted. 

The  target  is  round,  made  of  thick  brass,  hav- 
ing, to  strengthen  it  still  more,  a rib  raised  on 
the  edge,  which  also  protects  the  paint  from  being 
defaced. 

The  target  moves  easily  on  the  rod,  being  kept 
in  any  position  by  the  friction  of  the  two  fiat 
plates  of  brass  which  are  pressed  against  two  al- 
ternate sides,  by  small  spiral  springs,  working  in 
little  thimbles  attached  to  the  band  which  sur- 
rounds the  rod. 

There  is  also  a clamp  screw  on  the  back,  by 
which  it  may  be  securely  fastened  to  any  part  of 
the  rod. 

The  face  of  the  target  is  di voided  into  quad- 
rants, by  horizontal  and  vertical  diameters,  wliich 
are  also  the  boundaries  of  the  alternate  colors 
with  which  it  is  painted. 

Tlie  colors  usually  preferred  are  wdiite  and  red  : 
sometimes  white  and  black. 

The  opening  in  the  face  of  the  target  is  a little 
7^ 


78 


LEVELING  KODS. 


more  than  a tenth  of  a foot  long,  so  that  in  any  position  a tenth, 
or  a foot  figure,  can  be  seen  on  the  surface  of  the  rod. 

The  right  edge  of  the  opening  is  chamfered,  and  divided  into 
ten  equal  spaces,  corresponding  with  nine  hundredths  on  the  rod ; 
the  divisions  start  from  the  horizontal  line  which  separates  the 
colors  of  the  face. 

The  vernier,  like  that  on  the  other  side  of  the  rod,  reads  to 
thousandths  of  a foot. 

The  clamp,  which  is  screwed  fast  to  the  lower  end  of  the  upper 
sliding  piece,  has  a movable  part  which  can  be  brought  by  the 
clamp  screw  firmly  against  the  front  surface  of  the  lower  half  of 
the  rod,  and  thus  the  two  parts  immovably  fastened  to  each  other, 
without  marring  the  divided  face  of  the  rod. 


THE  POCKET  COMPASS. 


Fig,  17. 


This  little  instrument,  shown  with  Jacob  staff  socket  in  fig.  17, 
though  not  used  in  extensive  surveys  like  the  larger  compasses  we 
have  described,  is  found  very  convenient  in  making  explorations, 
or  in  retracing  the  lines  of  government  surveys,  as  in  locating  land 
warrants,  &c. 

The  sights  are  made  with  a slote  and  a hair,  on  opposite  sides ; 
they  also  have  joints  near  the  base,  so  as  to  fold  over  each  other 
above  the  glass,  when  the  compass  is  packed  in  its  case. 

The  circle  is  graduated  to  degrees,  and  figured  from  0 to  90 
each  way,  as  in  the  larger  instruments. 

The  needle  is  suspended  upon  a jeweled  centre,  and  is  raised  by 
the  lifter  shown  in  the  cut. 

The  Jacob  staff  socket  is  often  used  with  the  compass,  being 
screwed  to  the  under  side,  and  detached  at  pleasure. 

The  mountings  are  all  that  are  furnished,  the  staff  itself  being 
easily  made  out  of  a common  walking  stick. 

We  make  two  sizes  ol  the  pocket  compass,  differing  mainly  in 
the  needle,  which  in  one  is  two  and  a half,  in  the  other  three  and 
a half  inches  long. 


GENERAL  MATTERS. 


TPLIFODS. 

In  the  tripods  of  all  our  instruments,  the  upper  part  of  the  leg 
IS  flattened,  and  fitted  closely  in  the  surfaces  of  the  brass  cheek 
pieces. 

The  cheeks  are  made  very  bix)ad,  and  gife  a firm  hold  upon 
the  leg,  which  may  be  tightened  at  any  time  by  screwing  up  the 
bolts  which  pass  through  tlie  top  of  the  legs;  this  is  especially 
necessary  after  the  surface  of  the  wood  has  been  mucli  worn. 

The  legs  are  round,  and  taper  in  each  direction  from  a swell, 
turned  about  one-third  the  way  down,  from  the  head  to  the  point. 

The  point,  or  shoe,  is  a tapering  brass  ferule,  having  an  iron 
end;  it  is  cemented,  and  riveted  firmly  to  the  wood. 

The  legs  of  all  our  tripods  are  about  four  feet  eight  inches  long, 
from  head  to  point.  We  make  three  sizes  of  tripods,  which  we 
will  now  separately  describe. 

1.  The  Compass  Tripod,  seen  in  part  in  the  cut  of  the  vernier 
transit  and  having  the  brass  plate  to  which  the  cheeks  are  attached, 
three  and  three-fourth  inches  in  diameter,  and  legs  which  are  about 
one  inch  at  the  top,  one  and  three-eighths  at  the  swell,  and  seven- 
eighths  at  the  bottom. 

The  legs  are  usually  made  of  cherry,  sometimes  of  mahogany, 
and  the  tripod  is  used  with  the  various  kinds  of  compasses,  and 
with  the  vernier  transit. 

2.  The  Medium  Sized  Tripod,  shown  with  the  surveyors’ 
transit,  and  liaving  a plate  of  same  diameter  as  above,  but  witli 
the  cheeks  made  considerably  broader,  by  curving  at  eacli  end  ; 
the  legs  beirrg  also  about  an  eiglitli  of  an  incli  larger  tlironghout. 

This  tri[)od  has  mahogany  logs,  and  is  used  with  the  surveyors’ 
transit,  the  liglit  engineers’  transit,  and  the  sixteen  inch  level. 


CHAINS. 


81 


3.  The  Heayy  Tkipod,  shown  with  the  engineers’  transit^ 
having  a brass  plate  of  four  and  one-fourth  inches  diameter,  with 
extended  cheek  pieces,  and  with  legs  one  and  three-eighths  of  an 
inch  at  the  top,  one  and  three-fourths  at  the  swell,  and  one  and 
an  eighth  at  the  point. 

The  heavy  size  has  also  mahogany  legs,  and  is  used  with  the 
engineers’  transit,  and  larger  leveling  instruments. 

Lacquering, 

All  instruments  are  covered  with  a thin  varnish,  made  by  dis- 
solving gum  shellac  in  alcohol,  and  applied  when  the  work  is 
heated. 

As  long  as  this  varnish  remains,  the  brass  surface  will  be  kept 
from  tarnishing,  and  the  engineer,  by  taking  care  not  to  rub  his 
instrument  with  any  dusty  cloth,  or  to  expose  it  to  the  friction  of 
his  clothes,  can  preserve  its  original  freshness  for  a long  time. 

Bronze  Finish, 

Instead  of  the  ordinary  brass  finish,  some  engineers  prefer  in- 
struments blackened  or  bronzed.  This  is  done  with  an  acid  prep- 
aration, after  the  work  has  been  polished,  and  gives  the  instrument 
a very  showy  appearance,  besides  being  thought  advantageous  on 
account  of  not  reflecting  the  rays  of  the  sun  as  much  as  the  ordi- 
nary finish. 

AVhen  well  lacquered,  the  bronzing  will  last  a considerable 
time,  but  as  soon  as  it  becomes  a little  worn  the  appearance  of  the 
instrument  is  much  worse  than  one  finished  in  the  usual  style. 


c h:  ^ I rr  s. 


Four  Pole  Chains. 

The  ordinary  surveyor’s  chain  is  sixty -six  feet,  or  four  poles 
long,  composed  of  one  liundred  links,  each  connected  to  the  other 
by  two  rings,  and  furnished  with  tally  marks  at  the  end  of  every 
ten  links. 


82 


CHAINS. 


We  make  our  chains  of  the  best  No.  8 iron  wire,  the  rings 
being  sawed  and  the  ends  of  the  link  filed  and  bent  close,  so  as  to 
avoid  kinking. 

A link  in  measurement  includes  a ring  at  each  end. 

The  handles  are  of  brass,  each  forming  part  of  the  end  link, 
and  connected  to  it  by  a nut,  by  moving  which  the  length  of  the 
chain  is  adjusted. 

The  tallies  are  also  of  brass,  and  have  one,  two,  three,  or  four 
notches,  as  they  are  ten,  twenty,  thirty  or  forty  links  from  either 
end ; the  fiftieth  link  is  rounded,  so  as  to  distinguish  it  from  the 
others. 

l^wo  Pole  Chains, 

A chain  of  two  rods,  or  thirty-three  feet  long,  is  often  used  by 
surveyors,  and  we  have  occasionally  made  our  four  pole  chains  so 
tliat  by  detaching  a steel  snap  in  the  middle,  the  parts  could  be 
separated,  and  the  handle  being  transferred  to  the  forty -ninth  link 
in  the  same  manner,  a two  pole  chain  is  readily  obtained. 

Engineers^  Chains 

Differ  from  the  common  or  Gunter’s  chain  in  that  the  links  are 
each  one  foot  long ; the  wire  is  also  much  stronger.  They  are 
fifty  or  one  hundred  feet  long,  furnished  with  handles  and  tallies, 
and  usually  with  a swivel  in  the  middle,  so  as  to  avoid  twisting. 

The  wire  of  our  Engineers’  chain  is  of  size  No.  5 or  6,  and  the 
whole  is  made  in  the  most  substantial  manner. 

In  the  place  of  the  round  rings  ordinarily  used,  we  have  lately 
substituted  in  these  chains  other  rings  of  an  oval  form,  and  find 
them  aljout  one-third  stronger,  when  made  of  the  same  kind  of  wire. 

Steel  Chains. 

These  are  often  preferred,  on  account  of  their  greater  lightness, 
and  are  made  of  any  desired  length ; their  cost  is  about  double 
that  of  iron  cliains. 

Tlie  wire  used  in  our  steel  chains  is  of  size  No.  10,  and  is  very 
fttlff  and  strong. 


TAPE  MEASUPvES. 


83 


Marking  Pins. 

With  the  chain  there  are  also  needed  ten  marking  pins  or  chain 
stakes,  made  of  stout  iron  wire,  about  twelve  inches  long,  pointed 
at  one  end  to  enter  the  ground,  and  formed  into  a ring  at  the 
other,  for  convenience  in  handling. 

The  length  of  a chain  should  always  be  taken  from  its  extreme 
ends,  so  that  the  pins  are  set  on  the  outside  of  the  handles. 

It  is  best  that  the  surveyor  carefully  lay  down  on  the  surface 
of  the  ground  the  length  of  his  chain  while  it  is  yet  new,  and 
mark  the  points  by  monuments,  the  position  of  which  wdll  not  be 
disturbed  by  the  frost  or  accident. 

He  will  thus  have  a standard  measure,  to  which  his  chain  may 
be  adjusted  in  case  of  alterations  lo  which  all  are  liable. 

In  using  the  chain  it  should  be  drawn  straight,  and  examined 
at  intervals  so  as  to  detect  and  remove  any  kinks  or  other  cause 
of  inaccuracy. 


TAPE  MEASURES. 


The  best  are  Chesterman’s  steel  tapes,  made  of  a thin  ribbon  of 
steel,  which  is  jointed  at  intervals,  and  wound  up  in  a leathern 
case,  having  a folding  handle. 

These  tapes  are  of  all  lengths,  from  thirty-three  to  one  hundred 
feet,  divided  into  inches  and  links,  or  more  usually,  tenths  of  a 
foot,  and  links,  the  figures  and  graduations  being  raised  on  the 
surface  of  the  steel. 

The  great  cost  of  the  steel  tape  has  always  prevented  its  gen- 
eral use,  and  the  metallic  tape  of  the  same  manufacturer  is  the 
only  one  commonly  employed  in  American  Engineering. 

These  are  of  linen,  and  have  also  fine  brass  wires  interwoven 
through  their  whole  length. 

They  are  thus  measurably  correct,  even  when  wet. 

They  are  mounted  like  the  steel  tapes,  of  like  lengths,  and 
similarly  graduated. 


TABLE  OF  CONTENTS. 


Page. 

Adjustments  of  Compass, 12 

Vernier  Transit, 31 

“ “ Surveyors’  “ 51 

“ **  Leveling  Instrument, 69 

“ “ spirit  levels, 12 

“ “ needle, 12 

“ line  of  collimation  in  Transit, 31 

“ “ ‘‘  Level, 10 

“ “ standards,  to  make  tel.  trace  vertical  line, 85 

“ “ level  on  telescope, 51 

“ vertical  circle, 36 

“ “ object-glass  slide^ 69 

“ bubble  tube, 1l 

“ “ the  v/yes, . . . 7 1 

Ball  and  socket, 14.-37 

Ball  compound  tangent, 37 

Builders’ level, 75 

Bronze  finish, 81 

Centre  pin,  how  sharpened,  IS 

Chains,  4 pole  or  Gunters, 81 

“ 2 “ 82 

“ 100  feet  or  engineers, 82 

steel, 82 

Compass,  plain, 10 

“ vernier, 18 

“ railroad, 44 

pocket, 79 

Cross  wire  ring, 24 

Cross  wires,  how  replaced, 39 

Clamp  and  tangent, 20 


TABLE  OF  CONTENTS. 


Page. 

Drawing  instruments — see  “ supplement,” 89 

“ paper,  “ “ 

Electricity  on  compass  glass, 15 

Eye  piece,  how  composed, 23 

“ “ “ centred, 35 

Excellencies  of  the  Vernier  Transit, 40 

Farm  level, 15 

Glass  of  Compass,  how  replaced, 16 

General  matters, 80 

Ground  levels, 57 

Jaeob-staff  socket, 11 

Levels,  how  replaced, 16 

Leveling  screws, 50 

“ instrument, 63 

“ rods,  Boston, 76 

“ “ New  York, 76 

Lever  tester, 66 

Line  of  no  variation, 20 

Local  attraction, 42 

Lacquering, 81 

Marking  pins, 83 

Masons’  Level 75 

Micrometer, 58 

Needle  magnetic, 9 

“ “ how  I’emagnetized, 15 

“ “ variation  of  diurnal, 43 

“ “ “ “ secular, 3 9 

“ “ imperfections  of, 42 

Needle  instruments, 42 

Object-glass,  how  composed, 23 

“ “ slide,  how  adjusted, 69 

Parallax  instrumental, .......  28 

“ huw  avoided, 38.-65 


TABLE  OF  CONTENTS. 


Page. 

Pinion  to  eye  glass, 5$ 

Pocket  Compass, 79 

Repairs  of  Compass,  how  made, 15 

it  a Vernier  Transit, 39 

Sights  of  Compass, 11 

“ hair, 11 

" on  telescope, 31 

**  for  right  angles, 31 

Sensitiveness  of  a level  bubble,  degree  of, 66 

Shade  of  telescope, 56 

Spring  Catch, 14.-37 

Tangent  Scale  on  sights, 11 

Telescope  of  transit,  sectional  view  of, 23 

“ “ level,  “ “ 64 

“ magnifying  power  of,  how  ascertained, 28 

optical  principles  of, 25 

Transit,  vernier, 22 

“ surveyors’, 48 

” engineers’, 55 

Tripod  head,  light, 50 

“ “ heavy, 57 

**  legs,  different  sizes  of, 80 

Two  telescope  instrument, 61 

Theodolite  axis, 60 

Target, 77 

Tapes,  measuring,  steel  and  metallic, 83 

Vertical  circle, 80 

Vernier  of  compass, 19 

“ “ “ how  read, 19 

Watch  telescope, 59 

Wyes  of  level, 66 

Weight  of  Compasses,  plain, 17 

“ “ “ Vernier, 21 

“ “ Vernier  Transit, 41 

“ “ Surveyors’  “ 63 

“ “ Engineers’  “ 69 

“ “ TiCveling  Instrument, 76 


SUPPLEMENT  TO  MANUAL. 


DRAWING  INSTRUMENTS. 

To  guide  the  surveyor  and  engineer  in  the  selection  of  Drawing 
Instruments,  we  here  add  a detailed  description,  with  illustrations 
and  prices  of  the  separate  pieces,  and  cases  of  the  different  kinds 
in  general  use. 

Those  we  shall  first  mention  are  of  German  and  French  manu- 
facture, are  of  good  quality  and  finish,  and  such  as  the  great 
majority  of  purchasers  select  and  use. 

The  Swiss  instruments  are  of  better  quality  and  finish,  and  are 
held  a‘t  much  higher  rates. 

The  prices  given  with  all  the  instruments  described  are  the 
same  as  those  of  other  importers. 

FREIS'CH  AND  GERMAN  INSTRUMENTS. 


II 


DRAWING  INSTRUMENTS. 


FIGURE. 

1.  Brass  Dividers,  brass  joints,  rivet-beads,  5 inch  12  cts  , 6 inch 
1.  “ “ steel  joints,  screw-heads,  6 inch  25  cts.,  6 inch 

1.  Fine  Dividers,  steel  joints,  turned  cheeks,  4 inch  50  cts,,  5 inch 

62  cts.,  6 inch,  - - - - - - 

2.  Fine  Dividers,  steel  joints,  hair  spring,  5 inch  |1,00,  6 inch 

2.  “ “ “ superior,  5 incli  $1,37,  6 inch 

1.  German  Silver,  steel  joints,  turned  cheeks,  superior,  5 inch,  - 

1.  “ “ . A'  “ 6 inch,  - 

2.  hair  spring,  fine,  5 inch  $1,50,  6 inch 

2.  “ “ superior,  5 inch  $1,75, 6 inch 

3.  Three  legged  Dividers,  brass,  $2,62,  Ger.  Silver,  $2,75  to 

Bisecting,  German  Silver,  $1,00  to 

4.  Pocket  Dividers,  German  Silver,  ...... 

5.  Proportional  Compasses,  brass,  $1,50  to  $3;  full  divided  $7  to 

5.  “ “ German  Silver,  $7,25  to 

6.  Pillar  Compasses,  brass,  $5,50  and  $5,75,  Ger,  Silver,  $8,75  and 

7.  Dividers,  brass,  3 inch,  with  pen  and  pencil  point,  med.  quality, 

7.  Ger.  Silver,  “ fine  ‘‘ 


0 


8.  Dividers,  brass,  5 inch,  mcd.  quality,  with  pen  and  pencil  point, 

6 ineli,  - 

8.  “ 5 inch,  mcd,  quality,  with  addition  of  length- 
ening bar, 

8.  Dividers,  German  Silver,  6 inch,  fine  quality,  pen,  pencil,  bar 

and  needle  ))oint, 

9.  Furniture  for  Beam  Cennpasscs,  bi-ass,  $3  ; with  adjusting  screw, 

9.  “ “ “ “ Oernian  Silver,  $4,25  to 


PRICE. 

$0,18 

,37 

,75 

1,37 

1,75 

,87 

1,75 

2,00 

3.50 

2.50 
2,00 

8.50 

9.00 

8.00 
1,25 

2.50 


,87 


,87 

3,25 

3,75 

5,00 


DRAWING  INSTRUMENTS. 


Ill 


BOW  PENS  AND  PENCILS,  SPACING  DIVIDERS  AND 
DRAWING  PENS. 


FIGURE. 


PRICE. 


10.  Bow  Pens,  brass,  50  cts.  to 

11.  “ “ with  joint  in  each  leg,  German  Silver, 

Bow  Pencils,  “ - - 

12.  Bow  Pens,  with  adjusting  screw,  brass,  $1,25  ; German  Silver, 

12.  “ “ “ and  hinges  to  pen,  brass,  - 


Gcn’man  Silver, - . _ 

12.  Bow  Pens  and  adj  screw  and  pencil  point,  German  Silver,  - 
12.  Bow  Pens  with  adjusting  screw,  German  Silver,  with  pencil 
and  needle  point  and  extra  pen  point,  . . . . 

18.  Bow  Pencils,  solid  steel,  German  Silver  or  Ivory  handles,  - 

14.  Spacing  dividers,  “ “ “ “ 

15.  Bow  Pens,  “ “ “ 

16.  Drawing  Pens,  25,  37  and 

17.  “ “ with  hinge, 


17.  “ ‘‘  “ and  protracting  pin,  62  and 

17.  “ “ “ “ extra  fine,  - - - 

17.  “ “ all  German  Silver  for  red  ink, 

18.  “ “ double  or  Railroad  Pens,  $1,75  and  - 

19.  Roulettes,  for  dotting  lines,  50,  62  and 


$1,25 

2,25 

2,25 

1,50 

1,50 

2.00 

2,25 


8.50 
1,75 

1.50 
1,75 

,50 

,50 

,75 

1,25 

,75 

2.50 
,76 


IV 


DRAWING  INSTRUMENTS. 


SQUARES,  PROTRACTORS,  &C. 


T]  / / /'/7 ^ 

4^^ 

FIGURE.  22 


23  PRICE. 


20.  Brass  Protractors,  assorted  sizes,  124  cts.  to  - - $1,50 

20.  “ “ with  steel  blade,  2 to  3 feet  long,  - 7,50 

20.  German  Silver  Proti*actors,  with  horn  centre  and  movable  arm, 

divided  to  4 degrees,  $4,  to 6,50 

20.  German  Silver  Protractors,  whole  circle,  horn  centre,  and  mo- 

vable arm,  divided  to  4 degrees,  $4,75  to  - - - 8,75 

21.  Horn  Protractors,  4 inch  124  cts.,  5 inch  25  cts.,  6 inch  - ,37 

22.  Ivory  Protractors  for  Engineers,  6 inch,  $1,50,  2,00  2,50,  and  3,00 

22.  “ “ “ “ 24  inch  wide,  very  superior,  6 

inches  long,  $3,50  and  . . . _ _ 5^00 

22.  Ivory  Protractors  for  Engineers,  12  inch,  extra  wide  and  full,  8,00 

Ivory  Scales,  6 inch,  usual  quality,  - - - ,62 

23.  Ivory  Scales,  12  inch,  chain  on  edge  only,  20x40,  30x50,  40x60, 

$2,25  to  ------  - 3,00 

23.  Ivory  Scales,  12  inch,  chain  on  edge  only,  50x100,  - 3,75 

“ “ 12  inch,  for  Architects,  2,25,  2,50,  3,00  and  - 3,25 

“ “ 12  incli,  16  scales  off  edge,  in  tenths,  or  twelfths, 

$3,50  and  4,00 

23.  Boxwood  Scales,  6 inch,  usual  quality,  . - - ,25 

22.  “ I’rotracting  Scales,  6 incli,  - ’ - - ,62 

23.  “ Scales,  12  incli  chain,  10  to  60  on  edge,  - 1.00 


“ “12  incli,  16  scales  off  edge,  in  tenths  and  twelfths,  1,50 

“ “ 12  inch  Arcliitects,  graduated  from  4 to  3 inches,  1,50 

“ “ 3 sided  chain,  giving  6 scales  all  on  edge,  $.150,  3,00 

Poxwood  Scales,  3 sided,  Architecis,  giving  12  scales  all  on 
edge,  $1,50  to 


3,00 


DKAY/ING-  INSTRUMENTS. 


V 


FIGURE,  PRICE. 

23.  Boxwood  Gunter  Scales,  1 foot,  37  and  75  cts,  two  feet,  - $0,75 

“ Pocket  Rules,  1 foot,  4 fold,  25  to  75  cts.  Ivory  do, 

62  cts.  to  - - - - - - - 2,00 

Paper  Scales,  18  inches  long,  in  sets  of  six,  graduated  from  -J-  to 

three  inches,  per  set,  - - - - - 1,25 


24.  T Squares,  wood,  witli  arm,  18  to  30  inches  long,  ‘ $0,75 

24.  “ “ and  swivel  head,  - - 1,25 

24.  “ “ “ “ “ “ and  brass  edges 

to  arm,  $1,75  to  - - - - - 2,75 

25.  Irregular  Curves,  various  sizes,  25  to  37  and  - • ,50 

26.  Ebony  Triangles.  37  cts.  Pear  wood  do.  - • ,25 

27.  German  Silver  Squares  and  Triangles,  50  cts.  to  - - 2,50 

28.  Pins  to  fasten  paper  to  the  drawing  board,  brass,  25,  37  and 

60  cts.  German  Silver,  per  dozen,  - - - ,60 

29.  Horn  Centres,  to  prevent  the  dividers  from  marking  the  paper,  ,18 


30 


31 


VI 


DRAWING  INSTRUMENTS. 


FIGURE. 

80.  Parallel  Rules,  Ebony,  6 incli  87  cts,  9 in.  62,  12  in.  75,  15  in. 

30.  “ Ivory,  6 inch,  _ . - . 

30.  “ “ Brass,  fine,  9 in  lU'iS,  12  in.  |2,50,  16  in  - 

“ “ on  rollers,  6 inch  $4,25,  12  inch, 

“ Ebony,  12  in  $2,62.  15  in.  $8,37,  18  in 

“ Ivory,  graduated  edges,  12  in. 

18  inch, 

81.  Pentagraphs  of  Ebony,  very  accurately  made, 

32.  “ of  Brass,  “ - 


PRICE. 

$1,00 

1,00 

3,12 

5,75 

4.00 
4,25 

6.00 

14.00 

22.00 


CASES  OF  MATHEMATICAL  DRAWING  INSTRUMENTS. 


33.  No.  636,  Morocco  case — small  German  Silver  Instruments — 

Needle  point,  4 inch  dividers,  fine  quality,  - 3,50 

33.  No.  25,  wood  box,  brass  instruments,  without  needle  points, 

medium  quality,  -----  1^25 

84.  No.  32,  wood  box,  brass  instruments,  5 inch  dividers,  medium 

quality,  box  scale,  -----  1^75 

34.  No.  33,  wood  box,  brass  instruments,  G inch  dividers,  medium 

quality,  Ivory  scale,  - - - - 2,25 

34.  No.  600,  Morocco,  brass  instruments,  common  quality,  box 

protractor,  (fig.  22),  -----  3,50 

85.  No.  154,  Morocco,  German  Silver  instruments,  fine  quality, 

Iv(u-y  |)rotrac1or,  (22),  -----  3,50 

35.  No  o54,  Mo!occo,  German  Silver  instruments,  with  addition 

of  lengthening  bar,  - - - - - 4,25 

35.  No  61.),  Morocco,  German  Silver  instruments,  without  plain 
dividers, 


8,00 


DRAWINa  INSTRUMENTS. 


VII 


FIGURE. 

85.  No.  023,  Morocco  box,  brass  instruments,  good  quality, 

35.  No.  599,  “ “ “ “ common  quality,  box 

protractor, 


PRICE. 

|2,50 

1,25 


36.  No.  '736,  Morocco  box,  German  Silver  instruments,  fine  quality 

Ivory  pi-otractor,  -----  6,50 

37.  No.  745,  Morocco  box,  German  Silver  instruments,  fine  quality,  6,50 


38.  No.  15,  wood  box,  brass  instruments,  medium  quality.  - 3,50 

39.  “ 29,  “ “ “ needle  points,  ined.  qual.  3,75 

39,  “ 39,  **  “ with  bow  pen,  4,25 

39.  “ 40,  wood  box,  brass  instruments,  needle  points,  with  bow 

pen  and  proportional  compasses,  - - - G,00 

39.  No.  585,  Morocco  case,  brass  instruments,  fine  quality,  - 5,50 


yiii 


DRAWING  INSTRUMENTS. 


40.  No.  305,  wood  box,  German  Silver  instruments,  fine  quality,  $10,00 
40.  “ 585,  “ “ “ with  bow  pen,  13,00 

40.  “ 036,  “ “ **  “ and 

hair  dividers,  14,00 

41.  “ 845,  wood  box,  German  Silver  instruments,  fine  quality,  25,00 

41.  “ 655,  “ “ “ with  addition, 

of  Railroad  Pen,  (fig.  18)  - - - - 27,00 

41.  “ 455,  wood  box,  lock  and  key,  superior  quality,  without 

the  proportional  compasses,  but  with  double  drawing  pen, 

(fig,  18)  and  additional  pen,  (fig.  17)  - - 30,00 

41.  “ 126,  Avood  box,  lock  and  key,  German  Silver  instruments, 

superior  quality,  with  addition  of  Railroad  Pen,  (fig.  18) 
and  one  Pen,  (fig.  17)  - - - - 40,00 

4l.  “ 326,  same  as  No.  126,  but  with  addition  of  furniture  for 

Beam  Compasses,  (fig.  9)  - - - - 48,00 


42.  No.  5,  Fisli  slvin  cases,  brass  instruments,  box  scale,  - 2,50 

“ 55,  “ “ “ “ Ivory  scale,  - 2,76 

“ 57,  “ Ivory  scale,  steel  joints,  3,50 


German  Silver  Swiss  Drawing  Instruments. 


FIGURE.  PRICE, 

Xo,  1 A,  Drawing^  Compass,  joints  in  legs,  6-J  to  7 inches  long,  with 

pen,  pencil-holder,  needle  pt.,  lengthening  bar  and  dot.  pen,  $6,50 
Xo.  1 B,  Drawing  Compass,  6 inches  long,  with  pen,  pencil-holder, 

lengthening  bar  and  needle  point,  ...  5,00 

2.  Hair  Spring  Divider,  5-6  inch,  - _ - 2,00 

3.  Plain  Divider,  4^  inch,  . . - _ . 1,37-i 

3.  “ “ 5-6  “ ....  1,50 

4.  Hair  4^  “ - - - - - 1,75 

5.  Drawing  Compass,  4 in.,  with  pen,  pencil-holder  and  needle  pt.  4,00 

6.  Tlie  same,  without  the  needle  point,  - - 3,00 


X 


SWISS  INSTRUMENTS. 


FIGURE.  TRICE. 

Y.  Proporlianal  Compass,  with  full  divisions  for  lines  and  circles,  $8,00 
Y.  The  same,  with  Micrometer  Screw,  - - 9,00 

8.  Beam  Compass,  19-20  inches  long,  in  2 German  Silver  bars,  8,00 

8.  The  same,  20  inches  long,  in  3 German  Silver  bars,  - 9,00 

8.  “ “ 36  “ 4 “ “ “ - 10,00 

8.  “ “ 48  “ “ 4 “ “ “ - 12,50 

9.  Triangular  Compass,  - - - 3,00 

10.  Dotting  Pen,  - - - 1,Y5 

11.  Road  Pen,  - ^ - 2,50 

12.  Pocket  Divider,  - - - 1,Y6 

13.  Whole  and  Half  Divider,  - •*  - . 2^.50 

No.  14  A,  Universal  Compass,  with  points  to  shift,  - 4,50 

No.  14  B,  Universal  Compass,  with  points  to  turn,  - 5,00 


15.  Large  Steel  Spring  Divider, 

16.  Small  Steel  Stepping  Divider, 
lY.  Small  Steel  Compass,  with  Pen^ 
lY.  Small  Steel  Bow  Pencil, 

18.  Drawing  Pen,  with  joint  4^  inches  long, 

19.  “ “ “ 5i 

20.  “ “ 6 ** 


2,00 

1,25 

1,60 

1,50 

1,00 

1,25 

1,60 


SWISS  INSTRUMENTS.  XI 

FIGURE,  TRICE. 

21.  Horn  Centre,  with  German  Silver  frame,  - $0,37 

22.  Bow  Pen,  _ . . 1^80 

23.  Bow  Pen,  with  pencil  holder,  - - 2,50 

24.  German  Silver  Centre,  with  handle,  - ,37 

25.  German  Silver  Paper  Pins,  per  doz.,  - - ,60 

25.  Steel  “ “ “ - ,75 

A No.  26,  Calliper,  . - . . 4^00 

B English  pattern,  with  two  verniers,  - 7,00 

27.  Eccentric  Rule,  . . - 1^80 


28.  Protractor,  4^-  inch  diameter,  whole  degrees,  - 1,25 


28, 

5i 

half 

- 

- 

1,50 

28. 

It 

6 

half 

- 

1,62 

28. 

it 

quarter, 

- 

- 

2,50 

28.  Horn  Protractors,  from  25  to  - - ,50 

28.  Circular  Protractor  with  arm,  8 inch  diameter,  quarter  degrees,  8,00 
28,  “ 10  “ “ 10,60 


29.  Circular  Protractor  with  vernier,  8 inch  diam.,  qi  nrttr  deg.,  H,00 
2.9.  “ 10  “ “ 13,00 


XII 


SWISS  INSTRUMENTS. 


29.  Half  Circle  Protractor  with  rernier,  5 -i- inch  diam.,half  deg.  $7,50 

29.  “ “ “ 8 “ quarter  “ 9,00 

30.  Beam  Compass  furniture,  for  wood  beams,  - 6,00 

31.  33  and  34.  Horn  Curves,  each  - - ,50 

32.  Drawing  Compass,  4 inches,  with  long  Ivory  handle,  spring, 

and  micrometer,  with  2 pens,  pencil-holder  and  needle  pt.,  5,00 

35.  Parallel  Rule,  with  rollers,  - - 2,00 

36.  Protractor  Scale,  divided  to  -1°,  - - - 2,75 

36.  “ “ “ - - 3,75 

A No.  37.  Bow  Compass,  fast  needle  point  and  pen,  with  joints  in 

both  legs,  - - - - 2,00 

B No.  37.  Bow  Comj)ass,  fast  needle  point  and  pencil-holder,  with 

joints  in  both  legs,  - - - 2,00 

38.  Lengthening  Comj)as3,  . - - 12,00 

Persons  desiring  a comjdete  Case  have  but  to  name  the  numbers  of  the 
Jnstrumenfs  tlicy  want  in  the  Box, 

Tlio  price  of  the  Box  is  always  according  to  the  size  and  finish  of  the 
same. 


DRAWING  PAPER,  COLORS,  ETC 


111  filling;  orders  for  instruments  in  different  parts  of  the  country, 
We  have  frequently  been  called  upon  to  furnish  in  addition,  the 
Various  materials  for  the  office  work  of  the  Surveyor  and  Engineer, 
as  Drawing  Paper,  Colors^  Text  Books,  &c. 

We  have  therefore  supplied  ourselves  with  an  assortment  of 
these  goods,  and  shall  hereafter  be  able  to  furnish  them  on  as 
favorable  terms  as  any  other  dealers  in  the  Union. 


WHATMAN’S  TURKEY  MILL  DRAWING  PAPERS. 


Demy, 

. . . .20x15*  inches, 

$1,12 

Mfidiiirrij . , . 

22x17 

do  

do  

1,50 

Royji.l  . . 

. . .24x19 

do  . V . 

. do  . . . . 

2,06 

Sup-er-Royal, . 

...  27x19 

do  

2,25 

Tmppvinlj  - . . 

30x21 

d o . - 

3,37 

Elephant, . 

28x22 

do  

3,37 

Columbier, . .. 

. . . 34x23 

do  

5,25 

A tins  

.3.^x2^ 

do  

5,25 

Double  Elephant,  40x26 

do  

6,00 

Antiquarian, . 

....52x31 

do  ........... 

25,50 

. DRAWING  PAPER  IN 

ROLLS, 

Any  Length. 

No  1,  5-1  inches  wide,. . 

^^o.  2,  54 

do 

do  ...  .28 

do 

Xo.  3,  57 

do  heavy, . 

do 

TRACING  PAPERS. 

Demy,  

inches, 

$1,12 

Ooliimhipr. . . . 

do  

do 

3 37 

Double  Elephant,  40x26 

do  

do 

4,50 

9* 


XIV 


DRAWING  AND  TRACING  PAPERS,  ETC, 


VELLUM,  OR  TRACING  CLOTH, 

Any  Length. 

Clarified, 36  inches  wide, per  yard,. , . .75  cent^'. 

Extra  Finish,  English,  36  do  do  do  ...  .56  do 

Common, 36  do  do  do  ....50  do 

PROFILE  PAPER. 

No.  1,  ruling  42x15  in. — horizontal  ruling  20  to  in.,,  .per  sheet, . .36  cents. 
No.  2,  do  42xl3J  do  do  25  do  do  36  do 

do  21xl3| — 15  do  do  20 — 25  do  18  do 

CROSS  SECTION  PAPERS. 

Trautwine’s  Cross  Section  and  Diagram,  10  feet  to  inch,  for  Embankments 
of  14  and  24  feet,  roadway,  and  for  Excavations  of  18  and  28  feet, 


ruling  19fxl2  inches, per  sheet,.  . . .15  cents. 

Cross  Section,  ruling  22x16  inches,  8 ft.  to  inch, ...  do  ...  .15  do 

Ruled  and  Section, ..  ..22x17  do  9 do  do  ...  10  do 

Topographical  Ruled,  15x12  do  5 do  do  3 do 

FIELD  BOOKS. 

Level  Books,. each. . . .50  cents. 

Transit  do  do  ...  .50  do 

Record  do  do  ...  .60  do 

Paint  Stones,  3 holes  and  slide,  3x4-|-  in.,  37  cts. ; 3}x5,  50  cts. ; 4x6,  62  cts. 
Flat  Camel-hair  Brushes,  1 in.  18  cts. ; 1^  in.  25 ; 2 in.  31  ; 2-^  in.  38  ; 3 in.  44. 

Sable  Pencil  do  in  quill, per  doz.,. ..  .$1,25 

Camel-Hair  do  do  do  37-J  cents. 

Erasing  Knives, each....37-J  do 


NEWMAN’S  WATER  COLORS. 

Per  Cake  37^  Cents^ 

Brown,  Rose,  Scarlet,  Indian  Yellow, 

Pink,  and  Crimson,  and  Intense  Brown. 

Purple  Madder,  Purple  Lake, 

Per  Cake  75  Cents,  Half-Cake  37^  Cents. 

Cannine,  Cobalt  Blue,  Ultra  Marine, 

Scarlet,  Intense  Blue,  Lemon  Yellow, 


DRAWING  AND  TRACING  PAPERS,  ETC. 


X 


NEWMAN’S  WATER  COLORS. 


Per  Cake  25  Cents, 


Lamp  Black, 

Prussian  Green, 

Vandyke  Brown, 

Light  Red, 

Purple, 

Venetian  Red, 

Naples  Yellow, 

Raw  Sienna, 

Verdigris, 

Neutral  Tint, 

Raw  Umber, 

Verditer, 

Olive  Green, 

Red  Lead, 

Vermilion, 

Chrome  Yellow, 

Roman  Ochre, 

Yellow  Ochre, 

Payne’s  Grey, 

Sap  Green, 

Prussian  Blue, 

Terra  Verde, 

Yellow  Lake, 

Hooker’s  Green,  Nos.  1 & 

Cologne  Earth, 

Burnt  Sienna, 

Burnt  Umber,  [2. 

Antwerp  Blue, 

Flake  White, 

Indigo, 

Ivory  Black, 

King’s  Yellow, 

Gamboge. 

When  desired,  mahogany  boxes,  packed  with  6,  12,  18  and  24  cakes, 
are  furnished  without  additional  charge. 


are  furnished  without  additional  charge. 

OSBORNE’S  WATER  COLORS. 

Mahogany  Boxes,  36  colors,  $6,25;  30  colors,  $5,25:  24  colors, $4,25 

do  do  18  do  3,25;  12  do  2,25;  6 do  1,25 


Mahogany  and  Rose  Wood  Chests,  with  Lock,  Drawer,  Paint  Stone,  Water 
Glass,  India  Ink,  Brushes,  and  12  colors,. . . . $6,00. 
do  do  do  do  18  do  ....  7,50. 

do  do  do  do  24  do  ....  10,00. 

INDIA  INK,  &c. 

India  Rubber,  best  quality, each,.  . . .6  to  25  cents. 

India  Ink,  best  quality, 12-J-  cents  to  $1,50 


do  liquid,  in  bottles, 50  cents. 

Mouth  Glue, 8 do 


MAPPING  PENS. 

Gillott’s, per  doz.,. . . .50  cents. 

do  Lithograph  Crow  Quill, do  ....60  do 

LEAD  PENCILS. 

A.  W.  Faber’s  Polygrades  (Genuine). 

Hexagon  Gilt,  Nos.  1,  2,  3,  4,  6, per  doz., $1,00 

Black  or  Red  Gilt,  Round,  1,  2,  3,  4, do  ....  ,60 

Black  or  Yellow  Gilt,  Round,  1,  2,  8,  4,  small, do  ....  ,37 

One  Box  containing  7 Pencils,  for  Engineers,  sliding  ends  to  box,.  . . . ,62 

do  do  7 do  BB  to  HIIH, ^66 

do  do  4 do  Nos.  1 to  4, ,26 


LIST  OF  BOOKS 

ON 

CIVIL  ENGINEERING,  SURVEYING,  &c. 


PRlCEfi. 

GILLESPIE’S  Land  Surveying.  The  best  and  latest 

work  published. — [See  Advertisement.].  * . . . $2,00 

GILLESPIE’S  Manual  of  Roadmaking, , . . 1,50 

HEATHER’S  Treatise  on  Mathematical  Instruments.  An 
English  elementary  work.  Weales^  series  . . . 

LAW  & BURNELL’S  Engineering, * . 1,50 

HAUPT’S  Bridge  Construction, 3,00 

SMITH’S  Topography, ’ 2,00 

DOBSON’S  Masonry  and  Building,  1,13 

MAHAN’S  Civil  Engineering, , . . 3,00 

“ Industrial  Drawing, 2,00 

STEVENSON’S  Marine  Surveying  and  Hydrometry,. . . 4,00 

SIMMS  on  Levelling.  By  J.  H.  Alexander, ...  * 1,50 

Manual  for  Practical  Surveyors.  E.  W.  Beans, ,75 

Engineers’  Pocket  Companion  for  the  Field.  By  Grisw^old,  1,25 

Engineers’ Pocket  Table  Book.  By  Scribner, 1,25 

Engineers’  Field  Book.  Ileucks, 1,75 

Engineers’  Field  Book.  C.  S.  Cross, . . . * 1,00 

LYONS’  Tables  for  Excavations  and  Embankments. 

Per  Bheet,  25  ctH.  ; or  21  sheets,  bound  complete,.  . 7,50 


In  case  any  other  works  on  the  above  or  kindred  subjects 
should  be  de.sired  by  the  customer,  we  will  furni.sh  the  same  at 
Publishers’  prices. 

\V.  & L.  E.  (iURLEY, 

Troy,  N.  Y. 


Advertisement. 


PHILOSOPHICAL  APPARATUS  FOR  SCHOOLS, 
COLLEGES,  ETC. 


xlirPumiDS,  assorted  patterns  a.nd  sizes,  from  $8  to  $85  ; Glass  Receivers, 
Apple  Cutters,  Hemispheres,  Bell  in  Vacuo,  Air  Mills,  Revolving  Fans, 
Bursting  Squares,  Fountain  in  Vacuo,  Freezing  apparatus  &c.  &c.,  adapted 
to  the  pumps. 


ELECTRICAL  MACHINES. 


Plate  Electrical  Machines  IG  to  36  inch  plates,  $20  to  $125;  Leyden  Jars, 
Batteries,  Dischargers,  Dancing  Plates,  Chime  of  two  three  and  five  Bells, 
Electrometers,  Insulated  Stools,  Aurora  Tubes,  Electrical  Pistols,  Cannons, 
Orreries,  Heads  of  Hair  <fec..  Thunder  Houses,  Luminous  Words,  Misers^ 
Plates,  Egg  Stands,  Tin  Foil,  Amalgam,  Brass  Chain,  kc.  kc. 


Advertisement. 


MAGNETIC  APPARATUS. 


Horse  Shoe  Magnets,  Compound  and  Bar  Magnets,  Needles  on  Stands, 
Electro  Magnets,  Magnetic  Engines,  Telegraph  apparatus,  Groves’  and 
Smees’  Batteries,  Magnetic  Electrical  Machines  for  the  cure  of  nervous 
diseases,  &c.  &c. 

MAGIC  LANTEENS. 

A large  assortment  from  $2  to  $140  each.  Scripture,  Astronomical, 
Humorous,  Temperance,  Fire  Works  and  other  slides  in  every  variety. 

TELESCOPES  AND  SPY-GLASSES. 

Thermometers,  Barometers,  Hydrometers,  Rain  Gauges  &c. 

CAMERA  LTICIDAS  AND  CAMERA  OBSCURAS. 

Prisms,  Polyoramas,  Landscape  Mirrors,  Models  of  the  Eye  &c. 

MECHANICAL  POWERS  AND  GEOMETRICAL  FORMS. 

Inertia  apparatus,  Centre  of  Gravity  and  Centrifugal  force  apparatus; 
Dissected  Cones,  Cube  Root  Blocks,  Collision  Balls,  Atwood’s  Machine 
Gyroscope,  Models  of  Steam  Engines  &c. 

MICROSCOPES. 

A large  assortment,  simple  and  compound,  from  $1  to  $125. 

SPECTACLES. 

Spectacles  in  Gold,  Silver,  Steel  and  common  frames. 

Illustrated  and  priced  catalogues,  88  pages,  forwarded  by  Mail  gratis. 

JA.MES  W.  QXJEEIN, 

924  Chestnut  near  Tenth  St.,  Philada. 


Advertisement. 


31:0  AND  348  Broadway,  New  York. 


D.  APPLETON  AND  COMPANY 


HAVE  RECENTLY  PUBLISHED 

A TREATISE  ON  LAND  SURVEYING: 

THEORETICAL  AND  PRACTICAL. 

T3A’  AV.  M.  GJ-IILX.ESPIE,  EE.E. 

Prof,  of  Civil  Eng  ^ Union  College  ; Author  of Manual  of  Roads  and  Railways^"  t&c. 
1 Vol.  8 VO.— 424  Fag-es.— S2,00. 

With  Four  Hundred  Eni^ravings,  and  a Map  showing  the  Variation  of  the 
Needle  in  the  United  States. 


Among  the  leading  peculiarities  of  the  work  are  these : 

1.  All  the  operations  of  surveying  are  developed  from  only  five  simple 
principles. 

2.  A complete  system  of  surveying  with  only  a chain,  a rope,  or  any 
substitute,  is  fully  explained. 

3.  Means  of  measuring  inaccessible  distances,  in  all  possible  cases,  Avith 
the  chain  alone,  are  given  in  great  variety,  so  as  to  constitute  a Land 
Geometry.  It  occupies  26  pages,  with  58  figures. 

4.  The  Rectangular  method  of  Compass-surveying  is  greatly  simplified. 

5.  The  Traverse  Table  gives  increased  accuracy,  in  one-fifteenth  of  the 
space  of  the  usual  tables. 

6.  The  effect  of  the  changes  in  the  variation  of  the  needle,  on  the  re- 
survey  of  old  lines,  is  minutely  illustrated. 

7.  Correct  tables  of  the  times  of  elongation  of  the  North  Star  are  given  ; 
those  in  common  use  being  in  some  eases  nearly  half-an-hour  out  of  the  way. 

8.  The  adjustment  of  the  engineer’s  Transit  and  Theodolite  are  here,  for 
the  first  time,  fully  developed. 

9.  Methods  of  avoiding  obstacles  in  angular  surve3dng  occupy  24  pages, 
with  35  figures. 

10.  To[)ographical  Mapping  is  fully  de.scribed,  Avith  illustrations, 

11.  Laying  out,  l^arting  off,  and  Dividing  up  Land,  are  very  fully  ex- 
plained, and  illustrated  b^^  50  figures. 

12  The  most  recent  irnpi-oveinents  in  the  method.s  of  Surveying  the 
Public  Lands  of  the  United  States,  Avith  the  methods  used  for  marking 
“corners,”  are  minutely  described  from  official  authorities. 


Advertisement. 


A double  object  lias  been  kept  in  view  in  the  preparation  of  the  vol- 
lime,  viz:  to  make  an  introductory  treatise  easy  to  be  mastered  by  the 
young  scholar  or  the  practical  man  of  little  previous  acquirement,  the  only 
pre-requisites  being  Arithmetic  and  a little  Geometry  ; and,  at  the  same 
time,  to  make  the  instruction  of  such  a cliaracter  as  to  lay  a foundation 
broad  enough  and  deep  enough  for  the  most  complete  superstructure 
which  the  professional  student  may  subsequently  wiish  to  raise  upon  it. 

The  volume  is  divided  as  follows: 

Part  I.  Ge:  eral  Principles  and  Fundamental  Operations.  II.  Chain 
Surveying.  III.  Compass  Surveying.  IV.  Transit  and  Theodolite  Sur- 
veying. V,  Trigonometrical  Surveying.  VI  Trilinear  Surveying.  VII. 
Obstacles  in  Angular  Surveying.  VIII.  Plain  Table  Surveying  IX.  Sur- 
veying without  Instruments.  X.  Mapping.  XI.  Laying  out.  Parting  off, 
and  Dividing  up  Lands.  XII.  United  States’  Public  Lands. 

Appendix. — A.  Synopsis  of  Plane  Trigonometry.  B.  Demonstrations 
of  Problems.  C.  Leveling. 

Table.s. — Chords  for  Platting. — Latitudes  and  Departures. — Natural 
Sines  and  Cosines, 


EXTRACTS  FROM  LETTERS. 

From  Prof.  Chas.  W.  Hackley,  Cohimbia  College^  New  York. 

“ Prof.  Gillespie’s  woi-k  is  the  most  complete  one  in  our  language  on  the 
branches  of  surveying  of  which  it  treats.” 

From  Prof.  D.  LI.  Mahan,  West  Point  Academy. 

“1  have  received  Prof.  Gillespie’s  work  on  Surveying,  which  you  have 
had  the  kindness  to  send  me.  In  this  treatise  Prof.  Gillespie  has  given 
another  evidence  of  his  practical  acquaintance  with  the  wants  of  the 
teacher  and  })upil  in  his  sj>eeiality,  and  of  his  ability  to  meet  them.  His 
work,  which  presents  several  new  features  in  its  jdan,  is  written  with  such 
plainness,  ami  illustrated  with  such  co|)iousness  of  diagram  and  detail,  as 
cannot  fail  lo  render  the  subject  of  easy  attainment  to  the  most  ordinary 
comprehension.” 

From  Prof  E.  S.  Snell,  Amherst  College. 

“ Please  accept  my  thanks  for  the  copy  lately  received  of  Prof.  Gilles- 
[de’s  Surveying.  1 very  much  admire  its  systematic  character,  its  com- 
[>lctcncss  ami  fullness,  and  its  adaptcdne.^s  in  all  respects  to  the  wants  of 
the  teacher,  the  pupil,  and  the  joractical  Surveyor.  1 have  seen  no  work 
which  can  at  all  be  brought  into  comparison  with  it.” 

From  Prof.  Aug.  \V.  S.viitu,  Wesleyan  University. 

“ On  examination,  J fitnl  it  the  most  fidl  ami  complete  of  any  work  on 
I’ractical  Surveying  with  whi(th  I am  ac(|uaintcd  It  fuimishes  informa- 
tion, minute  and  specilic.,  on  all  points  wliich  arc  likely  to  occur  iu  prnc- 

I ice I know  of  no  belter  work,  or  om*  bettor  mla[)ted  to  the  wants 

of  tlio.se  who  liuve  not  tlic  aid  of  the  living  teacher.” 


Advertisement. 


From  y W.  Andrews,  President  of  Marietta  College^  Ohio. 

“From  my  knowledge  of  the  author,  I was  prepared  to  expect  a work 
of  decided  excellence,  and  certainly  I have  not  been  disappointed.  .... 
I shall  take  great  pleasure  in  recommending  it  to  all  who  wish  a full 
knowledge  of  surveying.” 

From  A C.  Roe,  Principal  of  Cornveall  Collegiate  School. 

“ I thank  the  author  for  the  time  and  labor  it  has  saved  me,  and  express 
the  great  sd,tisfaction  with  which  I have  used  it.  Valuable  in  its  plan  and” 
the  happy  manner  in  which  the  principles  of  the  science  are  unfolded,  it 
is  still  more  so  in  those  practical  hints  which  I have  seen  in  no  other  work, 
and  Which^  though  of  the  greatest  importance  even  to  a beginner,  I learned 
myself  only  after  a long  time,  and  very  considerable  experience.” 


SCIENTIFIC  WORKS 
Published  by  D.  Apppleton  & Co. 

APPLETON.  Dictionary  of  Mechanics,  Machines,  Engine 
Work,  and  Engineering,  containing  over  400*)  illustrations, 
and  nearly  2000  pages.  Complete  in  2 vols  large  8vo 

Strongly  and  neatly  bound, $12,00 

— Mechanics’  Magazine  and  Engineers’  Jour- 
nal. Vols.  I,  II  and  III,  for  1851-52-53, Cloth,  each,  3,50 

Cyclopaedia  of  Drawing,  for  Engineers, 

Mechanics,  and  Architects.  Edited  by  W.  E.  Worthern.  1 

volume,  royal  8vo (in  press) 

ALLEN’S  Philosophy  of  the  Mechanics  of  Nature.  Illus- 
trated. 8 VO “ 3,50 

BARTOL’S  Treatise  on  the  Marine  Boilers  of  the  United 

States.  8vo cloth,  l,5o 

BASSNETT’S  Theory  of  Storms.  1 vol.  12  mo.  Clotli,  1,00 

BOURNE’S  Catechism  on  the  Steam  Engine Cloth,  ,Y5 

— Treatise  on  the  Screw  Propeller.  New 

Edition.  1 vol.  4to Cloth,  9,00 

CLEAVELAND  & BACKUS’S  New  Work  on  Cottage 

and  Farm  Architecture.  1 handsome  vol.  8vo.,  with  loO  fine 

engravings Extra,  Cloth,  2,00 

COLE’S  Contractors’  Book  for  Working  Drawings  of 

Machinery.  Folio Cloth,  10,00 

COMING’S  Class-Book  of 'Physiology.  12mo 1,00 

DOWNING,  A.  J.  Architecture  of  Country  Houses. 
Including  Designs  for  Cottages,  Farm  Houses,  and  Villas  ; with 
remarks  on  Interiors,  Furniture,  and  the  best  modes  of  Warm- 
ing and  Ventilating.  With  320  Illustrations  1 vol.  8vo.  Cl.,  4,00 
FIELD’S  City  Arcliitecture.  8vo.,  with  20  engravings,  2,00 
FRY’S  Complete  Treatise  on  Artificial  Fish  Breeding. 

12mo Cloth,  ,75 


Advertisement. 


GILLESPIF]'S  (Prof.)  Practical  Treatise  on  Surveying. 

1 vol.  8 VO.  with  400  engravings, 

GREEN  & CONGDON.  Analytical  Class-Book  of  Bo- 
tany. Illustrated.  1 vol.  4to 

Primary  Class-Book  of  Botany. 

Illustrated.  4to 

HAUPT,  H.  Theory  of  Bridge  Construction.  With 

Practical  Illustrations.  8vo Cloth, 

HENCK’S  Field-Book  for  Railroad  Engineers.  I vol. 

12mo Tuck, 

JEFFERS.  Theory  and  Practice  of  Naval  Gunnery.  8vo. 

illustrated, 

JOHNSTON’S  Chemistry  of  Common  Life.  Illustrated. 

2 vols.  12ino Cloth, 

or  in  sheep, 

LAFEVER.  M.  Beauties  of  Modern  Architecture.  48 


plates,  8 vo 

LESLIE’S  Handbook  of  Painting.  I vol.  I2mo.  Illus- 
trated. Cloth, 

LYELL’S  Manual  of  Geology.  8vo.  Illustrated.  Cloth, 

In  sheep, 

Principles  of  Geology.  I large  vol.  8vo. 

Illustrated.  Cloth,  2,25.  In  sheep, 

OVERMAN,  F.  Metallurgy  ; embracing  Elements  of  Min- 
ing Operations,  AnaB'zation  of  Ores,  &c.,  8vo.  Illust’d.  Cloth, 
OWENS’  Treatise  on  the  Construction  of  Plank  Roads, 

12mo Cloth, 

REYNOLDS,  L.  E.  Treatise  on  Handrailing,  20  plates, 

8vo 


TEMPLETON,  W.  Mechanic,  Millwright,  and  Engineer’s 

Pocket  Coinpanion,  With  American  additions.  16mo 

Tuck 


TIRE,  DR.  Dictionary  of  Arts,  Alanufactures,  and  Mines, 


New  edition,  greatly  enlarged.  2 vols.  8vo Cloth, 

tSheep, 

W A RING’S  Elements  of  Agriculture.  A Book  for 
Young  Farmers.  With  questions  for  the  Use  of  Schools. 
12mo. Cloth, 


YOUMANS,  E.  L.  Class-Book  of  Chemistry.  12mo. 
Chart  of  Chemistry,  on  Roller,.  . . 


Cheinicy 
Alcohol] 


lias.  4 to Cloth, 

d |tlRRill^1l^ti(}|lioT 


Man.  12m(). a.  .Cvl 


YOUMANS’  Domestic  f^Lonomy.jyj|^  ^ 


UNivwjiiiY  ar 


2,00 

1.50 

3.00 

1,^6 

2.50 

2.00 

2.25 

4.00 

3.00 
1,75 

2.00 

2,50 

5.00 
,50 

2.00 

1,1)0 

1.25 

5.00 

6.00 

,75 

,75 

5.00 

2.00 

,50 


i 


f 


f 


X • 


